Asymmetric anodes for lithium-based energy storage devices

ABSTRACT

A method of making an anode for use in an energy storage device is provided. The method includes providing a current collector having an electrically conductive substrate and a surface layer overlaying a first side of the electrically conductive substrate. A second side of the electrically conductive substrate includes a filament growth catalyst, wherein the second side is opposite the first. The method further includes depositing a lithium storage layer onto the surface layer using a first CVD process forming a plurality of lithium storage filamentary structures on the second side of the electrically conductive substrate using second CVD process.

CROSS REFERENCE TO RELATED APPLICATION

This application claims the benefit of priority of U.S. ProvisionalApplication No. 62/891,496, filed Aug. 26, 2019, which is incorporatedherein by reference in its entirety for all purposes.

TECHNICAL FIELD

The present disclosure relates to lithium ion batteries and relatedenergy storage devices.

BACKGROUND

Silicon has been proposed for lithium-ion batteries to replace theconventional carbon-based anodes, which have a storage capacity that islimited to ˜370 mAh/g. Silicon readily alloys with lithium and has amuch higher theoretical storage capacity (˜3600 to 4200 mAh/g at roomtemperature) than carbon anodes. However, insertion and extraction oflithium into the silicon matrix causes significant volume expansion(>300%) and contraction. This can result in rapid pulverization of thesilicon into small particles and electrical disconnection from thecurrent collector.

The industry has recently turned its attention to nano- ormicro-structured silicon to reduce the pulverization problem, i.e.,silicon in the form of spaced apart nano- or micro-wires, tubes,pillars, particles and the like. The theory is that making thestructures nano-sized avoids crack propagation and spacing them apartallows more room for volume expansion, thereby enabling the silicon toabsorb lithium with reduced stresses and improved stability compared to,for example, macroscopic layers of bulk silicon.

Despite research into various approaches batteries based primarily onsilicon have yet to make a large market impact due to unresolvedproblems.

SUMMARY

There remains a need for anodes for lithium-based energy storage devicessuch as Li-ion batteries that are easy to manufacture, robust tohandling, high in charge capacity and amenable to fast charging, forexample, at least 1 C, and long in charge/discharge cycle lifetime.

In accordance with an embodiment of the present disclosure, a method ofmaking an anode for use in an energy storage device includes providing acurrent collector having an electrically conductive substrate and asurface layer overlaying a first side of the electrically conductivesubstrate. A second side of the electrically conductive substrateincludes a filament growth catalyst, wherein the second side is oppositethe first side. The method further includes depositing a lithium storagelayer onto the surface layer using a first CVD process forming aplurality of lithium storage filamentary structures on the second sideof the electrically conductive substrate using a second CVD process.

The present disclosure provides anodes for energy storage devices thatmay have one or more of at least the following advantages relative toconventional anodes: improved stability at aggressive ≥1 C chargingrates; higher overall areal charge capacity; higher charge capacity pergram of silicon; improved physical durability; simplified manufacturingprocess; and more reproducible manufacturing process. Anodes and energystorage devices of the present disclosure may also have otheradvantages.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a cross-sectional view of an anode according to someembodiments of the present disclosure.

FIG. 2 is a cross-sectional view of a prior art anode havingnanostructures.

FIG. 3A is a cross-sectional view of an electrically conductivesubstrate according to some embodiments of the present disclosure.

FIG. 3B is a cross-sectional view of an electrically conductivesubstrate according to some embodiments of the present disclosure.

FIG. 4 is a cross-sectional view of lithium storage filamentarystructures according to some embodiments of the present disclosure.

FIG. 5A is a cross-sectional view of a current collector having corefilaments according to some embodiments of the present disclosure.

FIG. 5B is a cross-sectional view of an anode according to someembodiments of the present disclosure.

FIG. 6 is a cross-sectional view of an anode according to someembodiments of the present disclosure.

FIG. 7 is a cross-sectional view of an anode according to someembodiments of the present disclosure.

FIG. 8 is a cross-sectional view of a battery according to someembodiments of the present disclosure.

FIG. 9A is a top-view SEM of an anode having a lithium storage layeraccording to an embodiment of the present disclosure

FIG. 9B is a cross-sectional SEM of the anode of FIG. 9A.

FIG. 10 is a top-view SEM of an anode having lithium storage filamentarystructures according to an embodiment of the present disclosure

DETAILED DESCRIPTION

It is to be understood that the drawings are for purposes ofillustrating the concepts of the disclosure and may not be to scale.Various aspects of anodes of the present disclosure, including metaloxide layers, deposition of lithium storage material, additional layersand methods are described in co-pending U.S. patent application Nos.16/285,842, 16/909,008, 16/991,613, 16/991,623, and 16/991,626, theentire contents of which are incorporated by reference for all purposes.

Anode Overview

FIG. 1 is a cross-sectional view according to some embodiments of thepresent disclosure. Anode 100 includes current collector 101. Currentcollector 101 includes a surface layer 105 overlaying a first side 103-1of an electrically conductive substrate 103. A lithium storage layer 107overlays the surface layer, and a plurality of lithium storagefilamentary structures 122 are in contact with a second side 103-2 ofthe electrically conductive substrate, the second side opposite thefirst side.

As described in more detail below, in some embodiments, the electricallyconductive substrate 103 may be a conductive foil or mesh, e.g., oneincluding copper, nickel, titanium, stainless steel, or a conductivecarbon. As described in more detail below, in some embodiments, thesurface layer may include a metal oxide, for example, an oxide ofnickel, copper, or titanium. In some embodiments, the surface layer mayinclude a metal chalcogenide, for example, a sulfide or polysulfide ofcopper or nickel. As described in more detail below, in someembodiments, the lithium storage layer may include at least 40 atomic %of silicon, germanium, or a combination thereof. In some embodiments,the lithium storage layer may be porous and/or continuous, e.g., acontinuous porous lithium storage layer. In some embodiments, thelithium storage filamentary structures may include silicon, germanium,tin, or a combination thereof. In some embodiments, the lithium storagefilamentary structures may include nanostructures such as nanowires ornanopillars. In some embodiments, the lithium storage layer or thelithium storage filamentary structures, or both, may be deposited orformed using a chemical vapor deposition (CVD) process including, butnot limited to, hot-wire CVD or a plasma-enhanced chemical vapordeposition (PECVD). In some embodiments the lithium storage layer may bedeposited using the same or different CVD process as used to form thelithium storage filamentary structures. In some embodiments, the lithiumstorage layer may be deposited concurrently with formation of thelithium storage filamentary structures, or in a separate step. In someembodiments, a surface layer having a metal oxide may favor depositionof silicon in the form of a continuous porous lithium storage layer anda surface having bare metal such as nickel may favor formation ofsilicon in the form of lithium storage filamentary structures, evenunder identical conditions.

In some embodiments, the lithium storage layer may be substantially freeof nanostructures, e.g., in the form of spaced-apart wires, pillars,tubes or the like, or in the form of regular, linear vertical channelsextending through the lithium storage layer The term “nanostructure”herein generally refers to an active material structure (for example, astructure of silicon, germanium or their alloys) having at least onecross-sectional dimension that is less than about 2,000 nm, other than adimension approximately normal to an underlying substrate (such as alayer thickness) and excluding dimensions caused by random pores andchannels. Similarly, the terms “nanowires”, “nanopillars” and“nanotubes” refers to wires, pillars and tubes, respectively, at least aportion of which, have a diameter of less than 2,000 nm. “High aspectratio” nanostructures have an aspect ratio greater than 4, where theaspect ratio is generally the height or length of a feature (which maybe measured along a feature axis aligned at an angle of 45 to 90 degreesrelative to the underlying current collector surface) divided by thewidth of the feature (which may be measured generally orthogonal to thefeature axis). In some embodiments, the lithium storage layer isconsidered “substantially free” of nanostructures when the anode has anaverage of fewer than 10 nanostructures per 1600 square microns (inwhich the number of nanostructures is the sum of the number ofnanowires, nanopillars, and nanotubes in the same unit area), suchnanostructures having an aspect ratio of 4:1 or higher. Alternatively,there is an average of fewer than 1 such nanostructures per 1600 squaremicrometers. Note that in some embodiments, the current collector mayhave a high surface roughness or the surface layer may includenanostructures, but these features are separate from the lithium storagelayer.

In some embodiments, deposition conditions are selected in combinationwith the surface layer so that the lithium storage layer is relativelysmooth providing an anode with diffuse or total reflectance of at least10% at 550 nm, alternatively at least 20% (measured at the lithiumstorage layer side). In some embodiments, the lithium storage layer sideof the anode may have lower reflectance than cited above, for example,by providing a current collector having a rough surface or by modifyingdeposition conditions of the lithium storage layer.

The anode can be a continuous foil or sheet but can alternatively be amesh or have some other 3-dimensional structure. In some embodiments,the anode is flexible.

Electrically Conductive Substrate

In some embodiments, the electrically conductive substrate includes ametallic material. In some embodiments, the metallic material includes atransition metal. In some embodiments, the metallic material includestitanium (or its alloys), nickel (or its alloys), copper (or itsalloys), or stainless steel. In some embodiments, the electricallyconductive substrate includes an electrically conductive carbon, such ascarbon black, graphene, graphene oxide, reduced graphene oxide graphite,carbon nanotubes, or fullerene. In some embodiments the electricallyconductive substrate may be in the form of a foil or sheet of conductivematerial, or alternatively a mesh structure or fabric-like structure, oralternatively a multilayer structure (discussed below). In someembodiments the electrically conductive substrate may have aconductivity of at least 10³ S/m, or alternatively at least 10⁶ S/m, oralternatively at least 10⁷ S/m, and may include inorganic or organicconductive materials or a combination thereof.

In some embodiments, the electrically conductive substrate has anaverage thickness (measured between first side and second side) of atleast 0.1 μm, alternatively at least 1 μm, alternatively at least 5 μm.In some embodiments, the electrically conductive substrate has anaverage thickness in a range of 0.1 μm to 1 μm, alternatively 1 μm to 2μm, alternatively 2 μm to 5 μm, alternatively 5 μm, to 10 μm,alternatively 10 μm to 15 μm, alternatively 15 μm to 20 μm,alternatively 20 μm to 30 μm, alternatively 30 μm to 50 μm,alternatively 50 μm to 100 μm, or any combination of contiguous rangesthereof.

In some embodiments, the electrically conductive substrate includes amultilayer structure. For example, as shown in FIG. 3A, electricallyconductive substrate 103 may include a first electrically conductivelayer 103 a in contact with a second electrically conductive layer 103 bhaving a different chemical composition than the first electricallyconductive layer 103 a. The surface of electrically conductive layer 103a corresponds to the first side 103-1 of the electrically conductivesubstrate 103, and the surface of electrically conductive layer 103 bcorresponds to the second side 103-2 of electrically conductivesubstrate 103. The first or second electrically conductive layer mayinclude any of the materials mentioned above for use in the electricallyconductive substrate. They may have the same or different thickness orsurface roughness. In some embodiments, the first electricallyconductive layer includes copper and the second electrically conductivelayer includes nickel. Although not shown, an electrically conductivesubstrate may include additional electrically conductive layers inbetween the first and second electrically conductive layers.

In some embodiments, as shown in FIG. 3B, electrically conductivesubstrate 103 may include an electrically insulating layer 104 providedbetween a first electrically conductive layer 103 c and a secondelectrically conductive layer 103 d. The surface of electricallyconductive layer 103 c corresponds to the first side 103-1 of theelectrically conductive substrate 103, and the surface of electricallyconductive layer 103 d corresponds to the second side 103-2 ofelectrically conductive substrate 103. The first or second electricallyconductive layer may include any of the materials mentioned above foruse in the electrically conductive substrate, and they may be the sameor different with respect to chemical composition, thickness, or surfaceroughness. The two sides separated by an insulating layer may enable thelithium storage layer to be electrically addressable independently ofthe lithium storage filamentary structures, which may allow for greateroverall battery operational flexibility. For example, the operatingvoltage or current on one side may be optimized for high charge capacityand the other may be optimized for high charging rates. In someembodiments, the operating voltage on one side may be within 20%, 10%,or 5% of the operating voltage for the other side. Insulating layer 104may include a polymer, a glass, a ceramic, or some other electricallyinsulative material. In some embodiments, the insulating layer 104includes a thermally stable material capable of temperature excursionsthat may be used for forming the surface layer, the lithium storagelayer or the lithium storage filamentary structures, e.g., any loss inmanufacturing yield attributable to thermal degradation of theinsulating layer is less than 10%. In some embodiments, the insulatinglayer comprises a material that is thermally stable for at least 30minutes at a temperature in a range of 50° C. to 150° C., alternatively150° C. to 250° C., alternatively 250° C. to 350° C., alternatively 350°C. to 450° C., alternatively 450° C. to 550° C., alternatively 550° C.to 650° C., or any combination of contiguous ranges thereof.

Surface Layer

The surface layer should be sufficiently electrically conductive (e.g.,is at least semi-conducting, or non-insulating) to allow transfer ofelectrical charge between the electrically conductive substrate and thelithium storage layer. The surface layer may include dopants thatpromote electrical conductivity.

In some embodiments, the surface layer has an average thickness of atleast 0.002 μm, alternatively at least 0.005 μm, alternatively at least0.010 μm, alternatively at least 0.020 μm, alternatively at least 0.050μm, alternatively at least 0.1 μm, alternatively at least 0.2 μm, oralternatively at least 0.5 μm. In some embodiments, the surface layerhas an average thickness in a range of about 0.002 μm to about 10 μm,alternatively in a range of about 0.002 μm to about 0.010 μm,alternatively in a range of about 0.010 μm to about 0.050 μm,alternatively in a range of about 0.005 μm to about 0.10 μm,alternatively in a range of about 0.10 μm to about 0.40 μm,alternatively in a range of about 0.40 μm to about 0.70 μm,alternatively in a range of about 0.70 μm to about 1.0 μm, alternativelyin a range of about 1.0 μm to about 2.0 μm, alternatively in a range ofabout 2.0 μm to about 5.0 μm, alternatively in a range of about 5.0 μmto about 10 μm, or any combination of contiguous ranges thereof.

The surface layer may include two or more sublayers having differentchemical compositions.

When forming or depositing the surface layer or sublayers on the firstside 103-1 of the electrically conductive substrate 103, the second side103-2 may be oriented, covered, treated, or coated (e.g., with aremovable material such as an organic polymer), to prevent unwanteddeposition or formation of metal oxide or metal chalcogenide on thesecond side

Metal Oxide Surface Layer

In some embodiments, the surface layer includes a metal oxide. In someembodiments, the surface layer may include or be referred to as a metaloxide layer. The metal oxide layer may include a stoichiometric oxide, anon-stoichiometric oxide, or both. In some embodiments, the metal withinthe metal oxide layer may exist in multiple oxidation states. The metaloxide layer may include a mixture of metal oxides having homogeneouslyor heterogeneously distributed oxide stoichiometries, mixtures ofmetals, or both. In some embodiments, the metal oxide layer may have agradient of oxygen content where the atomic % of oxygen adjacent to anelectrically conductive substrate is lower than the atomic % adjacent tothe lithium storage layer. The metal oxide layer may include dopants orregions of unoxidized metal that promote electrical conductivity.

In some embodiments, the metal oxide layer includes a transition metaloxide, e.g., an oxide of nickel, titanium, or copper. In someembodiments, the metal oxide layer includes an oxide of aluminum. Insome embodiments, the metal oxide layer is an electrically conductivedoped oxide, including but not limited to, indium-doped tin oxide (ITO)or an aluminum-doped zinc oxide (AZO). In some embodiments, the metaloxide layer includes an alkali metal oxide or alkaline earth metaloxide. In some embodiments, the metal oxide layer includes an oxide oflithium. As mentioned, the metal oxide layer may include mixtures ofmetals. For example, an “oxide of nickel” may optionally include othermetals in addition to nickel. In some embodiments, the metal oxide layerincludes an oxide of an alkali metal (e.g., lithium or sodium) or analkaline earth metal (e.g., magnesium or calcium) along with an oxide ofa transition metal (e.g., nickel or copper). In some embodiments, themetal oxide layer may include a small amount of hydroxide such that theratio of oxygen atoms in the form of hydroxide relative to oxide is lessthan 0.25.

In some embodiments, surface layer 105 includes a metal oxide (a “metaloxide-containing surface layer”) and is formed directly by atomic layerdeposition (ALD), a CVD process, evaporation, or sputtering onto thefirst side 103-1 of the electrically conductive substrate 103. Thesecond side 103-2 may be oriented, covered, treated, or coated in someway, e.g., with a removable polymer, to prevent unwanted deposition onthe second side. In some embodiments, the electrically conductivesubstrate 103 includes a metal, at least at the first side 103-1, and ametal oxide-containing surface layer 105 is formed by oxidizing aportion of the metal at the first side 103-1 of the electricallyconductive substrate 103. For example, the metal can be thermallyoxidized in the presence of oxygen, electrolytically oxidized,chemically oxidized in an oxidizing liquid or gaseous medium or the liketo form a metal oxide-containing surface layer 105. The second side103-2 may be oriented, covered, treated, or coated in some way, e.g.,with a removable polymer, to avoid unwanted metal oxide formation. Insome embodiments, the second side 103-2 of the electrically conductivesubstrate 103 may include a material that does not readily oxidize toform a metal oxide.

In some embodiments, a metal oxide layer precursor composition may becoated or printed over the first side 103-1 of the electricallyconductive substrate 103 then treated to form a metal oxide-containingsurface layer 105. Some non-limiting examples of metal oxide precursorcompositions include sol-gels (metal alkoxides), metal carbonates, metalacetates (including organic acetates), metal hydroxides, and metal oxidedispersions. The metal oxide precursor composition may be thermallytreated to form the metal oxide layer. In some embodiments, roomtemperature may be sufficient temperature to thermally treat theprecursor. In some embodiments, a metal oxide precursor composition isthermally treated by exposure to a temperature of at least 50° C.,alternatively in a range of 50° C. to 150° C., alternatively in a rangeof 150° C. to 250° C., alternatively in a range of 250° C. to 350° C.,alternatively in a range of 350° C. to 450° C., or any combination ofthese ranges. Thermal treatment time depends on many factors, but mayoptionally be at least 0.1 minute, alternatively in a range of 1 to 120minutes, to form the metal oxide layer. In some embodiments, thermaltreatment may be carried out using an oven, a tube furnace, infraredheating elements, contact with a hot plate or exposure to a flash lamp.In some embodiments, the metal oxide precursor composition is treated byexposure to reduced pressure to form the metal oxide, e.g., to drive offsolvents or volatile reaction products. The reduced pressure may be lessthan 100 Torr, alternatively in a range of 0.1 to 100 Torr. Exposuretime to the reduced pressure may optionally be at least 0.1 minute,alternatively in a range of 1 to 120 minutes. In some embodiments, bothreduced pressure and thermal treatment may be used.

In some embodiments, the metal oxide layer precursor compositionincludes a metal, e.g., metal-containing particles, that is treated withan oxidant (e.g., as previously described) under conditions where theoxide layer precursor is readily oxidized but underlying electricallyconductive substrate is less so. The metal oxide precursor compositionmay include a metal that is the same as or different from the metal(s)of the electrically conductive substrate. In some embodiments, multiplemetal precursor compositions may be used to form a pattern of differentmetal oxides or multilayer structure of different metal oxides.

In some embodiments, the metal oxide is formed in the same chamber as,or in line with, a tool used to deposit the lithium storage layer. Dopedmetal oxide layers can be formed by adding dopants or dopant precursorsduring the metal oxide formation step, or alternatively by addingdopants or dopant precursors to a surface of an electrically conductivesubstrate prior to the metal oxide layer formation step, oralternatively treating a metal oxide layer with a dopant or dopantprecursor after initial formation of the metal oxide layer. In someembodiments, the metal oxide layer itself may have some reversible orirreversible lithium storage capacity. In some embodiments, thereversible areal capacity of the metal oxide layer is lower than that ofthe lithium storage layer. In some embodiments, the metal oxide layermay be porous. In some embodiments, a porous metal oxide may have adensity lower than the density of a non-porous metal oxide. In someembodiments, the density of a porous metal oxide is in a range of 50% to60% of the density of a non-porous metal oxide, alternatively 60% to70%, alternatively 70% to 80%, alternatively 80% to 90%, alternatively90% to 95%, alternatively 95% to 99%, or any combination of contiguousranges thereof.

In some embodiments, the metal oxide may be provided in a pattern overthe first side 103-1 of electrically conductive substrate as disclosedin U.S. patent application Ser. No. 16/909,008, the entire contents ofwhich are incorporated herein.

In some embodiments, the metal oxide layer is formed by oxidizing asurface region of first side of metal-containing electrically conductivesubstrate, for example, oxidation of a first side of a metal foil suchas nickel foil, but not the second side. The non-oxidized portion of themetal foil acts as the electrically conductive substrate and theoxidized portion corresponds to the metal oxide layer. This method isamenable to high-volume and low-cost production of current collectors.The oxidation conditions depend upon the metal/metal surface, the targetoxide thickness and the desired oxide porosity. Unless otherwise stated,any reference to a particular metal includes alloys of that metal. Forexample, nickel foil may include pure nickel or any alloy of nickelwherein nickel is the primary component. In some embodiments, an alloymetal also oxidizes, and the oxide of nickel formed from the alloy mayinclude that corresponding oxidized metal. In some embodiments, thecurrent collector is formed by oxidation of a nickel substrate, e.g., anickel foil, in ambient air in a furnace brought to a temperature of atleast 300° C., alternatively at least 400° C., for example in a range ofabout 600° C. to about 900° C., or alternatively higher temperatures.The hold time depends upon the selected temperature and the desiredthickness/porosity for the metal oxide layer. Typically, the oxidationhold time will be in a range of about 1 minute to about 2 hours, butshorter or longer times are contemplated. A surface pretreatment stepmay be applied to promote or otherwise control oxidation. Other metalssuch as copper and titanium may have other operational hold times,temperatures and pretreatments according to their propensity to beoxidized.

Metal Chalcogenide Surface Layer

In some embodiments, the surface layer may include a metal chalcogenide.Herein, the term “metal chalcogenide” refers to a metal chalcogenidematerial that includes at least one of sulfur or selenium, and in someembodiments may include both. The metal chalcogenide material mayinclude a metal sulfide, a metal polysulfide, a metal selenide, or ametal polyselenide, or a mixture thereof. A metal sulfide may generallyrefer to a compound where the metal is associated with a sulfur atom inthe form of S²⁻. A metal polysulfide may generally refer to a compoundwhere the metal is associated with a chain of sulfur atoms in the formof S_(n) ²⁻ where n≥2. Similarly, a metal selenide may generally referto a compound where the metal is associated with a selenium atom in theform of Se²⁻. A metal polyselenide may generally refer to a compoundwherein the metal is associated with a chain of selenium atoms in theform of Se_(n) ²⁻ where n≥2. In some embodiments, metal chalcogenidesmay have complex structures. In some embodiments, the metal chalcogenidemay include a mixture of sulfur- and selenium-containing moieties. Inthe present disclosure, a surface layer may be considered to include: ametal sulfide so long as it includes a metal and least one identifiableS²⁻ species; or a metal selenide so long as it includes a metal and atleast one identifiable Se²⁻ species; or a metal polysulfide so long asit includes a metal and at least one identifiable S_(n) ²⁻ species withn≥2; or a metal polyselenide so long as it includes a metal and at leastone identifiable Se_(n) ²⁻ species with n≥2. A metal chalcogenideincluding (S_(m)Se_(p))²⁻ where m and p are each at least 1, may beequally referred to as a metal polysulfide or a polyselenide for thepurposes of this disclosure.

The chalcogenide may include a stoichiometric or non-stoichiometricmixture of elements with respect to the metal oxidation state. Thesurface layer may include a mixture of metal chalcogenides havinghomogeneously or heterogeneously distributed sulfur or selenium,mixtures of metals, or mixtures of metal oxidation states. In someembodiments, the metal chalcogenide material may include a transitionmetal sulfide, a transition metal polysulfide, a transition metalselenide, a transition metal polyselenide, or mixture thereof. Thetransition metal may be a single transition metal or a mixture oftransition metals. In some embodiments, the metal chalcogenide materialmay include at least one of Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, orIn.

In some embodiments, the metal chalcogenide material may include acopper sulfide, a copper polysulfide, a copper selenide, a copperpolyselenide, or a mixture thereof. The copper of the metal chalcogenidematerial may have an oxidation state of (I), (II) or a mixture of both.In some embodiments, the surface layer may include a copper chalcogenideaccording to formula 1:

Cu_(x)[S_(m)Se_(p)]  (1)

where 1≤x≤2, (m+p)≥1, and the average oxidation state of Cu=2/x. In someembodiments, a surface layer may include a copper chalcogenide offormula (1) in addition to some Cu(0) metal.

In some embodiments, the surface layer may further include one or moremetal oxides (for example, those described above) in addition to themetal chalcogenide. The metal element of the metal oxide may be the sameas that of the metal chalcogenide or different. In some embodiments, themetal oxide may be a transition metal oxide. In some embodiments, themetal oxide may include one or more of Ti, V, Cr, Mn, Fe, Co, Ni, Cu,Zn, Ga, or In. In some embodiments, the metal oxide may include lithium,optionally in addition to another metal. In some embodiments, thesurface layer may include a homogeneous or heterogeneous mixture of oneor more metal chalcogenides with one or more metal oxides.

In some embodiments, the surface layer may include an oxygen-containingcopper chalcogenide having the formula 2:

Cu_(x)[(S_(m)Se_(p))_(y)O_((1-y))]  (2)

where 1≤x≤2, (m+p)≥1, 0<y<1, and the average oxidation state of Cu=2/x.

In some embodiments, the surface layer may include two or moresublayers, at least one of which includes a metal chalcogenide having atleast one of sulfur or selenium. In some embodiments, the surface layermay include at least one sublayer having a sulfur- orselenium-containing metal chalcogenide and one sublayer having a metaloxide. In some embodiments, a first sublayer having a sulfur- orselenium-containing metal chalcogenide is disposed in contact with thefirst side 103-1 of electrically conductive substrate and a secondsublayer having a metal oxide is provided over the first sublayer and incontact with the lithium storage layer 107. In some embodiments, thesecond sublayer having the metal oxide is thinner than the firstsublayer. In some embodiments, the electrically conductive substrate mayinclude copper metal, and a surface layer may include a first sublayerof a copper sulfide or a copper polysulfide in contact with the coppermetal and a second sublayer of titanium dioxide over first sublayer.

In some embodiments, the surface layer may include a metal chalcogenidewherein the metal includes a mixture of a transition metal and lithium.

In some embodiments, the metal chalcogenide may be formed directly overthe first side 103-1 of the electrically conductive substrate by atomiclayer deposition (ALD), CVD, evaporation, or sputtering.

In some embodiments, the electrically conductive substrate includes ametal, at least at the first side 103-1, and the surface layer may beformed by treating a portion of the metal at the first side 103-1 of theelectrically conductive metal layer with an agent to form the metalchalcogenide, wherein at least some of metal chalcogenide includes themetal(s) of the electrically conductive substrate. In some non-limitingexamples, the reagent may be applied: a) as a vapor, e.g., vaporizedsulfur; b) from a reduced pressure system, e.g., sulfur from asulfur-valved cracker (VCC) effusion cell; c) from a solution, e.g.,liver of sulfur solution, or a solution including one or more of apolysulfide salt, a thiosulfate salt, or a polyselenide salt; d) bycontact with a reactive sulfur- or selenium-containing solid; or) byelectrochemical reaction in a solution comprising a sulfur or seleniumsource. Treating may further include a heating step.

In some embodiments, a metal oxide precursor layer is first formed onthe first side 103-1 of electrically conductive substrate and thentreated to first form the metal chalcogenide. The metal oxide precursorlayer may include a precursor that includes a metal oxide. The precursormay then be converted to the metal chalcogenide. Methods of forming ordepositing a metal oxide onto the electrically conductive substrate havebeen discussed above. Some or all of the metal oxide precursor layer maybe treated to cause sulfurization or selenization to form the metalchalcogenide material, for example, a metal sulfide, a metalpolysulfide, a metal selenide, or a metal polyselenide. In someembodiments, treatment of the metal oxide precursor layer includestreatment with a solution, e.g., one including one or more of a sulfidesalt, a polysulfide salt, a thiosulfate salt, a selenide salt, or apolyselenide salt. Treating may further include a heating step. In someembodiments, not all of the metal oxide of the metal oxide precursorlayer is converted and the surface layer may further include some metaloxide.

In some embodiments, a surface layer precursor composition may be coatedor printed over the first side 103-1 of electrically conductivesubstrate 103 then treated to form surface layer 105. A few non-limitingexamples of metal chalcogenide precursor compositions include sulfide-or selenide-sols, and sulfur- or selenide-containing organometalliccompounds. Treating may further include a heating step.

In some embodiments as mentioned above, forming the metal chalcogenidemay include a thermal treatment. Such treatment may include exposure toa temperature of at least 50° C., alternatively in a range of 50° C. to150° C., alternatively in a range of 150° C. to 250° C., alternativelyin a range of 250° C. to 350° C., alternatively in a range of 350° C. to450° C., or any combination of these ranges. Thermal treatment timedepends on many factors, but may optionally be at least 0.1 minute,alternatively in a range of 1 to 240 minutes, to form the desiredsurface layer. In some embodiments, thermal treatment may be carried outusing an oven, a tube furnace, infrared heating elements, contact with ahot plate or exposure to a flash lamp. In some embodiments, treatmentmay include exposure to reduced pressure to form the metal chalcogenide,e.g., to drive off solvents or volatile reaction products. The reducedpressure may be less than 100 Torr, alternatively in a range of 0.1 to100 Torr. Exposure time to the reduced pressure may optionally be atleast 0.1 minute, alternatively in a range of 1 to 240 minutes. In someembodiments, both reduced pressure and thermal treatment may be used. Insome embodiments, the reduced pressure or thermal treatment may initiatechemical reactions, drive off solvents, or remove reaction byproducts.

Lithium Storage Layer

The lithium storage layer includes a material capable of reversiblyincorporating lithium. A lithium storage layer may be porous. In someembodiments, a lithium storage layer may include silicon, germanium,tin, antimony, or a combination thereof. In some embodiments, a lithiumstorage layer is substantially amorphous. In some embodiments a lithiumstorage layer includes substantially amorphous silicon. Suchsubstantially amorphous storage layers may include a small amount (e.g.,less than 20 atomic %) of crystalline material dispersed therein. Alithium storage layer may include dopants such as hydrogen, boron,phosphorous, sulfur, fluorine, aluminum, gallium, indium, arsenic,antimony, bismuth, nitrogen, or metallic elements. In some embodiments alithium storage layer may include porous substantially amorphoushydrogenated silicon (a-Si:H), having, e.g., a hydrogen content of from0.1 to 20 atomic %, or alternatively higher. In some embodiments, alithium storage layer may include methylated amorphous silicon. Notethat, unless referring specifically to hydrogen content, any atomic %metric used herein for a lithium storage material or layer refers to allatoms other than hydrogen.

In some embodiments, a lithium storage layer includes at least 40 atomic% silicon, germanium or a combination thereof, alternatively at least 50atomic %, alternatively at least 60 atomic %, alternatively at least 70atomic %, alternatively, at least 80 atomic %, alternatively at least 90atomic %. In some embodiments, a lithium storage layer includes at least40 atomic % silicon, alternatively at least 50 atomic %, alternativelyat least 60 atomic %, alternatively at least 70 atomic %, alternatively,at least 80 atomic %, alternatively at least 90 atomic %.

In some embodiments, a lithium storage layer includes less than 10atomic % carbon, alternatively less than 5 atomic %, alternatively lessthan 2 atomic %, alternatively less than 1 atomic %. In someembodiments, a lithium storage layer includes less than 5% by weight ofcarbon-based binders, graphitic carbon, graphene, graphene oxide,reduced graphene oxide, carbon nanotubes, carbon black, and conductivecarbon.

In some embodiments, a lithium storage layer may be a porous lithiumstorage layer that includes voids or interstices (pores), which may berandom or non-uniform with respect to size, shape and distribution. Suchporosity does not result in, or result from, the formation of anyrecognizable nanostructures such as nanowires, nanopillars, nanotubes,nanochannels or the like. In some embodiments, the pores arepolydisperse. In some embodiments, when analyzed by SEM cross section,90% of pores larger than 100 nm in any dimension are smaller than about5 μm in any dimension, alternatively smaller than about 3 μm,alternatively smaller than about 2 μm. In some embodiments, the lithiumstorage layer may include some pores that are smaller than 100 nm in anydimension, alternatively smaller than 50 nm in any dimension,alternatively smaller than 20 nm in any dimension. In some embodimentsthe lithium storage layer has an average density in a range of 1.0-1.1g/cm³, alternatively 1.1-1.2 g/cm³, alternatively 1.2-1.3 g/cm³,alternatively 1.3-1.4 g/cm³, alternatively 1.4-1.5 g/cm³, alternatively1.5-1.6 g/cm³, alternatively 1.6-1.7 g/cm³, alternatively 1.7-1.8 g/cm³,alternatively 1.8-1.9 g/cm³, alternatively 1.9-2.0 g/cm³, alternatively2.0-2.1 g/cm³, alternatively 2.1-2.2 g/cm³, alternatively 2.2-2.25g/cm³, or any combination of contiguous ranges thereof, and includes atleast 40 atomic % silicon, alternatively at least 50 atomic % silicon,alternatively at least 60 atomic % silicon, alternatively at least 70atomic % silicon, alternatively 80 atomic % silicon, alternatively atleast 90 atomic % silicon, alternatively at least 95 atomic % silicon.

In some embodiments, the lithium storage layer may be a continuouslithium storage layer. In some embodiments, the lithium storage layermay be both continuous and porous (a continuous porous lithium storagelayer). The majority of active material (e.g., silicon, germanium, tin,antimony, or alloys thereof) of a continuous lithium storage layer hassubstantial lateral connectivity across portions of the currentcollector, such connectivity extending around random pores andinterstices (in the case of a continuous porous lithium storage layer).Referring again to FIG. 1, in some embodiments, “substantial lateralconnectivity” means that active material at one point X in thecontinuous lithium storage layer 107 may be connected to active materialat a second point X′ in the layer at a straight-line lateral distance LDthat is at least as great as the thickness T of the continuous lithiumstorage layer, alternatively, a lateral distance at least 2 times asgreat as the thickness, alternatively, a lateral distance at least 3times as great as the thickness. Not shown, the total path distance ofmaterial connectivity, including circumventing pores in the case of acontinuous porous lithium storage layer, may be longer than LD. In someembodiments, the continuous lithium storage layer may be described as amatrix of interconnected silicon, germanium, or alloys thereof, and inthe case of a continuous porous lithium storage layer, with random poresand interstices embedded therein. In some embodiments, the continuousporous lithium storage layer has a sponge-like form. In someembodiments, about 75% or more of the surface layer surface iscontiguous with the first lithium storage layer, at least prior toelectrochemical formation. It should be noted that a continuous lithiumstorage layer does not necessarily extend across the entire anodewithout any lateral breaks and may include random discontinuities orcracks and still be considered continuous.

The thickness or mass per unit area of the lithium storage layer(optionally continuous and/or porous) depends on the storage material,desired charge capacity and other operational and lifetimeconsiderations. Increasing the thickness typically provides morecapacity. If the lithium storage layer becomes too thick, electricalresistance may increase and the stability may decrease. In someembodiments, the anode may be characterized as having an active siliconareal density of at least 0.5 mg/cm², alternatively at least 1.0 mg/cm²,alternatively at least 1.5 mg/cm², alternatively at least 3 mg/cm²,alternatively at least 5 mg/cm². In some embodiments, the lithiumstorage structure may be characterized as having an active silicon arealdensity in a range of 0.5-1.5 mg/cm², alternatively 1.5-2 mg/cm²,alternatively in a range of 2-3 mg/cm², alternatively in a range of 3-5mg/cm², alternatively in a range of 5-10 mg/cm², alternatively in arange of 10-15 mg/cm², alternatively in a range of 15-20 mg/cm², or anycombination of contiguous ranges thereof. “Active areal silicon density”refers to the silicon in electrical communication with the currentcollector that is available for reversible lithium storage at thebeginning of cell cycling, e.g., after anode “electrochemical formation”discussed later. “Areal” of this term refers to the surface area of theelectrically conductive substrate over which active silicon is provided.In some embodiments, not all of the silicon content is active silicon,i.e., some may be tied up in the form of non-active silicides orelectrically isolated from the current collector.

In some embodiments the lithium storage layer has an average thicknessof at least 0.5 μm, alternatively at least 1 μm, alternatively at least3 μm, alternatively at least 7 μm. In some embodiments, the lithiumstorage layer (optionally continuous and/or porous) has an averagethickness in a range of about 0.5 μm to about 50 μm. In someembodiments, the lithium storage layer (optionally continuous and/orporous) comprises at least 85 atomic % amorphous silicon and has athickness in a range of 0.5 to 1 μm, alternatively 1-2 μm, alternatively2-4 μm, alternatively 4-7 μm, alternatively 7-10 μm, alternatively 10-15μm, alternatively 15-20 μm, alternatively 20-25 μm, alternatively 25-30μm, alternatively 30-40 μm, alternatively 40-50 μm, or any combinationof contiguous ranges thereof.

In some embodiments, the lithium storage layer (optionally continuousand/or porous) includes silicon but does not contain a substantialamount of crystalline silicides, i.e., the presence of silicides is notreadily detected by X-Ray Diffraction (XRD). Metal silicides, e.g.,nickel silicide, commonly form when silicon is deposited at highertemperatures directly onto metal, e.g., nickel foil. Metal silicidessuch as nickel silicides often have much lower lithium storage capacitythan silicon itself. In some embodiments, the average atomic % ofsilicide-forming metallic elements within the lithium storage layer areon average less than 35%, alternatively less than 20%, alternativelyless than 10%, alternatively less than 5%. In some embodiments, theaverage atomic % of silicide-forming metallic elements within thelithium storage layer are in a range of about 0.01% to about 10%,alternatively about 0.05 to about 5%. In some embodiments, the atomic %of silicide forming metallic elements in the lithium storage layer ishigher nearer the current collector than away from the currentcollector.

In some embodiments, the lithium storage layer, optionally a continuousand/or porous lithium storage layer, includes a sub-stoichiometric oxideof silicon (SiO_(x)), germanium (GeO_(x)) or tin (SnO_(x)) wherein theratio of oxygen atoms to silicon, germanium or tin atoms is less than2:1, i.e., x<2, alternatively less than 1:1, i.e., x<1. In someembodiments, x is in a range of 0.02 to 0.95, alternatively 0.02 to0.10, alternatively 0.10 to 0.50, or alternatively 0.50 to 0.95,alternatively 0.95 to 1.25, alternatively 1.25 to 1.50.

In some embodiments, the lithium storage layer, optionally a continuousand/or porous lithium storage layer, includes a sub-stoichiometricnitride of silicon (SiN_(y)), germanium (GeN_(y)), or tin (SnN_(y))wherein the ratio of nitrogen atoms to silicon, germanium or tin atomsis less than 1.25:1, i.e., y<1.25. In some embodiments, y is in a rangeof 0.02 to 0.95, alternatively 0.02 to 0.10, alternatively 0.10 to 0.50,or alternatively 0.50 to 0.95, alternatively 0.95 to 1.25.

In some embodiments, the lithium storage layer, optionally a continuousand/or porous lithium storage layer, includes a sub-stoichiometricoxynitride of silicon (SiO_(x)N_(y)), germanium (GeO_(x)N_(y)), or tin(SnO_(x)N_(y)) wherein the ratio of total oxygen and nitrogen atoms tosilicon, germanium or tin atoms is less than 1:1, i.e., (x+y)<1. In someembodiments, (x+y) is in a range of 0.02 to 0.95, alternatively 0.02 to0.10, alternatively 0.10 to 0.50, or alternatively 0.50 to 0.95.

In some embodiments, the above sub-stoichiometric oxides, nitrides, oroxynitrides may be provided by a CVD process, including, but not limitedto, a PECVD process. The oxygen and nitrogen may be provided uniformlywithin the lithium storage layer, or alternatively the oxygen ornitrogen content may be varied as a function of storage layer thickness.

In some embodiments, the lithium storage layer may include two or moresublayers, optionally continuous and/or porous lithium storage sublayershaving different physical properties or chemical compositions, andindependently selected from any of the embodiments discussed above.

Lithium Storage Filamentary Structures

In some embodiments, lithium storage filamentary structures 122 areformed in contact with the second side 103-2 of the electricallyconductive substrate 103. In some embodiments, the lithium storagefilamentary structures include a material capable of reversiblyincorporating lithium. In some embodiments, the lithium storagefilamentary structures may include a porous material. In someembodiments, the lithium storage filamentary structures may includesilicon, germanium, tin, antimony, or a combination thereof. In someembodiments, the lithium storage layer may exclude any of these elementsor combination of these elements. In some embodiments, the lithiumstorage filamentary structures 122 may include lithium storage nanowiresor nanopillars. In some embodiments, the lithium storage filamentarystructures may have an aspect ratio of at least 2. As shown in FIG. 4,the aspect ratio of a lithium storage filamentary structure refers tothe ratio of its maximum height H to its maximum width W. The maximumheight refers to how far the filament extends from the second side 103-2of the electrically conductive substrate, regardless of the currentcollector orientation. The maximum width is measured generallyorthogonal to the axis of the lithium storage filamentary structure. Theaxis may be the longitudinal axis of the lithium storage filamentarystructure or a branch or trunk of the lithium storage filamentarystructure. The axis may be an axis about which the lithium storagefilamentary structure is substantially symmetrical. In some embodiments,the maximum width may be the width of a cross-sectional slice of thelithium storage filamentary structure, where the cross-sectional slicehas the minimum area for a slice going through a given point of thelithium storage filamentary structure. In some embodiments, the maximumwidth may be measured in a direction parallel to the second side 103-2.

The lithium storage filamentary structures may take on a variety ofshapes. The width of the lithium storage filamentary structure may varyas a function of filament height. As shown in FIG. 4, in someembodiments, lithium storage filamentary structures 122 a may have abulbous end away from second side 103-2 of the electrically conductivesubstrate. The bulbous end has a width W that is greater than a widthcloser to or at the second side 103-2. In some embodiments, lithiumstorage filamentary structures 122 b may be wider near the second side103-2 of the electrically conductive substrate. In some embodiments,lithium storage filamentary structures 122 c may have a uniform width asa function of filament height or as a function of the length of thefilament from its point of attachment to second side 103-2. In someembodiments, lithium storage filamentary structures 122 d may bebranched, wherein maximum width 122 d-W is measured across the widesttrunk (as in this case) or branch. In some embodiments, lithium storagefilamentary structures 122 e may include a core filament 120, e.g., ametal or silicide nanowire, that may be more electrically conductivethan surrounding lithium storage material making up the lithium storagefilamentary structure.

The core filament may be characterized as having a width that may bemeasured in a plane parallel to the maximum width of the lithium storagefilamentary structures. In some embodiments when the core filamentincludes a metal silicide, the boundary of the core filament may be whenthe atomic concentration of metal falls to below 50% of the atomicconcentration at the center of the core filament, alternatively below20%, or alternatively below 10%. In some embodiments, the core filamentmay have a maximum width that is less than 50% of the maximum width ofthe lithium storage filamentary structure, alternatively less than 20%,alternatively less than 10%, alternatively less than 5%. In someembodiments, the core filament may have a height that is less than 99%of the height of the lithium storage filamentary structure,alternatively less than 90%, alternatively less than 70%, alternativelyless than 50%. Although not shown in FIG. 4, any of the other structures122 a, 122 b, 122 c, or 122 d may optionally include a core filament.

In some embodiments, at least some of the lithium storage filamentarystructures may have an aspect ratio of at least 2 (defined above),alternatively at least 3, alternatively at least 4, alternatively atleast 5, alternatively at least 7, alternatively at least 10. In someembodiments, the majority of the lithium storage filamentary structureshave an aspect ratio in a range of 3 to 5, alternatively in a range of 5to 10, alternatively in a range of 10 to 20, alternatively in a range of20 to 50, alternatively in a range of 50 to 100, or any combination ofcontiguous ranges thereof. The aspect ratio described herein mayrepresent the mean average, median, or mode of the lithium storagefilamentary structures. In addition, the aspect ratios may describe apercentage of the lithium storage filamentary structures, including atleast 50%, 60%, 70%, 80%, 90%, 95%, 99%, or 100% of the lithium storagefilamentary structures.

In some embodiments, at least some of the lithium storage filamentarystructures have a height of at least 0.2 μm, alternatively 0.5 μm,alternatively at least 1.0 μm, alternatively at least 3 μm,alternatively at least 5 μm, alternatively at least 10 μm. In someembodiments, at least some of the lithium storage filamentary structureshave a height of less than 500 μm, alternatively less than 250 μm,alternatively less than 100 μm, alternatively less than 75 μm,alternatively less than 50 μm, alternatively less than 25 μm,alternatively less than 20 μm, alternatively less than 15 μm,alternatively less than 10 μm, alternatively less than 7 μm. In someembodiments, the lithium storage filamentary structures collectivelyhave an average height in a range of 0.2 μm to 0.5 μm, alternatively ina range of 0.5 μm to 1 μm, alternatively in a range of 1 μm to 2 μm,alternatively in a range of 2 μm to 5 μm, alternatively in a range of 5μm to 10 μm, alternatively in a range of 10 μm to 20 μm, alternativelyin a range of 20 μm to 50 μm, alternatively in a range of 50 μm to 100μm, or any combination of contiguous ranges thereof. The heightdescribed herein may represent the mean average, median, or mode of thelithium storage filamentary structures. In addition, the heights maydescribe a percentage of the lithium storage filamentary structures,including at least 50%, 60%, 70%, 80%, 90%, 95%, 99%, or 100% of thelithium storage filamentary structures.

In some embodiments, at least some of the lithium storage filamentarystructures have a maximum width of at least 0.01 μm, alternatively 0.02μm, alternatively at least 0.05 μm, alternatively at least 0.1 μm,alternatively at least 0.25 μm, alternatively at least 0.5 μm,alternatively at least 1 μm, alternatively at least 2 μm, alternativelyat least 3 μm, alternatively at least 5 μm, alternatively at least 10μm, alternatively at least 20 μm, alternatively at least 50 μm. In someembodiments, at least some of the lithium storage filamentary structureshave a maximum width of less than 50 μm, alternatively less than 20 μm,alternatively less than 10 μm, alternatively less than 7 μm,alternatively less than 5 μm, alternatively less than 4 μm,alternatively less than 3 μm, alternatively less than 2 μm,alternatively less than 1 μm, alternatively less than 0.1 μm. In someembodiments, the lithium storage filamentary structures collectivelyhave a maximum width in a range of 0.01 μm to 0.02 μm, alternatively ina range of 0.02 μm to 0.05 μm, alternatively in a range of 0.05 μm to0.1 μm, alternatively in a range of 0.1 μm to 0.2 μm, alternatively in arange of 0.2 μm to 0.5 μm, alternatively in a range of 0.5 μm to 1 μm,alternatively in a range of 1 μm to 2 μm, alternatively in a range of 2μm to 5 μm, alternatively in a range of 5 μm to 10 μm, alternatively ina range of 10 μm to 20 μm, or any combination of contiguous rangesthereof. The widths described herein may represent the mean average,median, or mode of the lithium storage filamentary structures. Inaddition, the widths may describe a percentage of the lithium storagefilamentary structures, including at least 50%, 60%, 70%, 80%, 90%, 95%,99%, or 100% of the lithium storage filamentary structures.

In some embodiments, the lithium storage filamentary structures arebulbous lithium storage filamentary structures (for example, those like122 a of FIG. 4) and tightly packed, i.e., spaced very close to oneanother and often in contact. In some embodiments, at least 50%,alternatively at least 70%, alternatively at least 80%, alternatively atleast 90%, alternatively substantially all of bulbous lithium storagefilamentary structures are in contact with at least one other bulbouslithium storage filamentary structures, alternatively at least two otherbulbous lithium storage structures. In some embodiments, tightly packedbulbous lithium storage filamentary structures may be characterized ashaving a total reflectance of at least 10% measured at 550 nm,alternatively at least 15%, or alternatively at least 20%.

In some embodiments, lithium storage filamentary structures are nottightly packed and may be characterized as having a total reflectance ofat less than 10% measured at 550 nm, alternatively less than 8%.

In some embodiments, the lithium storage filamentary structures includesilicon, germanium, antimony, tin, or a combination thereof. In someembodiments, the lithium storage filamentary structures include atransition metal silicide or a transition metal alloy of germanium. Insome embodiments the lithium storage filamentary structures have a totalcontent of silicon, germanium, or a combination thereof, of at least 30atomic %, alternatively, at least 40%, alternatively at least 50%,alternatively at least 60%, alternatively at least 70%, alternatively atleast 80%, alternatively at least 90%, alternatively at least 95%. Notethat, unless referring specifically to hydrogen content, any atomic %metric used herein for a lithium storage filamentary structures refersto all atoms other than hydrogen.

Methods of growing lithium storage filaments may include, but are notlimited to, CVD and PECVD methods described in U.S. Pat. No. 9,325,014and U.S. Pat. No. 8,257,866, the entire contents of which areincorporated by reference for all purposes.

In some embodiments, the second side 103-2 of the electricallyconductive substrate 103 includes a filament growth catalyst material. Afilament growth catalyst material assists in initiating and growing thefilament. For the purposes of this disclosure, filament growth catalystmaterials include “true” catalytic materials that remain activeindefinitely, and materials that may eventually be consumed duringfilament growth. In some embodiments the filament growth catalystmaterial may be a vapor-liquid-solid (VLS) filament growth catalystmaterial. In some embodiments the filament growth catalyst material maybe provided as a substantially continuous layer that corresponds to thesecond side 103-2 of electrically conductive substrate 103. In someembodiments, the second side 103-2 of electrically conductive substrate103 may include a pattern of filament growth catalyst material where thepattern may be random or predetermined. In some embodiments theelectrically conductive substrate may be a metal foil that is itself afilament growth catalyst material, and the second side 103-2 ofelectrically conductive substrate 103 may simply be a clean surface ofthe foil. Non-limiting examples of catalyst materials may includenon-refractory transition metals and their alloys. The catalyst materialmay include, for example, nickel, gold, palladium, platinum, ruthenium,aluminum, indium, gallium, tin, or iron, or their alloys.

Referring to FIG. 5A, in some embodiments, growing lithium storagefilamentary structures may include growing a plurality of core filaments120 on the second side of the electrically conductive substrate. In someembodiments this is done by VLS method whereby the current collector isexposed to a filament precursor gas under elevated temperatures. Thetemperature depends on the catalyst and filament precursor gas, but insome embodiments may be at least 300° C., alternatively at least 400°C., alternatively from 300° C. to 400° C., alternatively at least from400° C. to 500° C., alternatively, at least from 500° C. to 600° C., oralternatively at least 600° C. In some embodiments, the filamentprecursor gas is a silicon-containing gas such as silane or agermanium-containing gas such as germane, but alternative silicon- andgermanium-containing gases may be used. In some embodiments, thefilaments include a silicide or germanium alloy. In some embodiments,conditions for growing the core filaments may also deposit a lithiumstorage layer 107 a comprising silicon or germanium or both. The corefilaments may be electrically conductive or semi-conductive. In someembodiments the filament growth catalyst material may include nickel andthe filaments include nickel silicide. In some embodiments, the filamentgrowth catalyst material may be consumed during formation of thefilaments.

As shown in FIG. 5B, in some embodiments, a plurality of lithium storagefilamentary structures 122 may be formed by depositing a lithium storagecoating 121 over the core filament 120. Lithium storage coating 121 mayhave a different chemical composition than core filament 120. In someembodiments, the lithium storage coating may include silicon, germanium,tin, or a combination thereof. In some embodiments, the lithium storagefilamentary structures are formed at least in part by a CVD (chemicalvapor deposition) process, such as Thermal CVD, HWCVD (hot-wire CVD),and/or PECVD (plasma enhanced chemical vapor deposition). In someembodiments, core filaments 120 may be grown by a thermal CVD processand lithium storage coating 121 may be deposited by HWCVD or PECVD. Thevapor deposition process may include a lithium storage precursor gasthat contains silicon (e.g., silane), germanium (e.g., germane), or tin(e.g., Sn(IV) tert-butoxide). In some embodiments, core filaments 120may be grown in a separate step or chamber than lithium storage coating121 deposition. In some embodiments, core filaments 120 may be grown inthe same chamber as used for depositing lithium storage coating 121. Insome embodiments, the growth of core filaments and formation of lithiumstorage filamentary structures 122 may be performed in a common stepwithout substantially changing conditions, e.g., by using a catalystthat is consumed, such that core filament formation stops and depositionof lithium storage coating 121 begins. That is, the core filamentformation may be self-limiting. Alternatively, conditions are alteredafter core filament growth (temperature, precursor gas, gas pressure,plasma power, deposition angle, or the like) to promote deposition oflithium storage coating 121 and formation of the lithium storagefilamentary structures 122. In some embodiments, the core filamentarystructures may include a metal silicide core filament 120 (e.g. a nickelsilicide) and a silicon-containing lithium storage coating 121 that mayalso contain some of the metal but at a lower atomic % than the corefilament. That is, the lithium storage coating 121 may have a higheratomic % silicon than the core filament 120. As shown in FIG. 4B, insome embodiments, conditions for depositing lithium storage coating 121,may also deposit lithium storage layer 107 b on the opposite side,thereby forming a lithium storage layer 107 having sublayers 107 a and107 b.

In some embodiments, the second side 103-2 of the electricallyconductive substrate 103 may include silicon-containing lithium storagefilamentary structures and have a total silicon content of at least 1mg/cm², alternatively at least 2 mg/cm², alternatively at least 3mg/cm², alternatively at least 10 mg/cm², alternatively at least 15mg/cm². In some embodiments, the second side 103-2 of the electricallyconductive substrate 103 may include silicon-containing lithium storagefilamentary structures and have an active areal silicon density in arange of 1-2 mg/cm², alternatively in a range of 2-3 mg/cm²,alternatively in a range of 3-5 mg/cm², alternatively in a range of 5-10mg/cm², alternatively in a range of 10-15 mg/cm², alternatively in arange of 15-20 mg/cm², alternatively in a range of 20-30 mg/cm²,alternatively in a range of 30-40 mg/cm², alternatively in a range of40-50 mg/cm², or any combination of contiguous ranges thereof. In someembodiments, not all of the silicon content is available for lithiumstorage and may be tied up in the form of silicides.

CVD

CVD generally involves flowing a precursor gas, a gasified liquid interms of direct liquid injection CVD or gases and liquids into a chambercontaining one or more objects, typically heated, to be coated. Chemicalreactions occur on and near the hot surfaces, resulting in thedeposition of a thin film on the surface. This is accompanied by theproduction of chemical by-products that are exhausted out of the chamberalong with unreacted precursor gases. As would be expected with thelarge variety of materials deposited and the wide range of applications,there are many variants of CVD that may be used to form the lithiumstorage layer, the lithium storage filamentary structures, the surfacelayer, a supplemental layer (see below) or other layer. It may be donein hot-wall reactors or cold-wall reactors, at sub-torr total pressuresto above-atmospheric pressures, with and without carrier gases, and attemperatures typically ranging from 100-1600° C. in some embodiments.There are also a variety of enhanced CVD processes, which involve theuse of plasmas, ions, photons, lasers, hot filaments, or combustionreactions to increase deposition rates and/or lower depositiontemperatures.

As mentioned, the lithium storage layer or lithium storage filamentarystructures, e.g., containing silicon, germanium, tin, or a combination,may be provided by plasma-enhanced chemical vapor deposition (PECVD).Relative to conventional CVD, deposition by PECVD can often be done atlower temperatures and higher rates, which can be advantageous forhigher manufacturing throughput. In some embodiments, the PECVD may beused to deposit a substantially amorphous silicon material (optionallydoped). In some embodiments, PECVD is used to deposit a substantiallyamorphous continuous porous silicon layer over the surface layer.

PECVD

In PECVD processes, according to various implementations, a plasma maybe generated in a chamber in which the substrate is disposed or upstreamof the chamber and fed into the chamber. Various types of plasmas may beused including, but not limited to, capacitively-coupled plasmas,inductively-coupled plasmas, and conductive coupled plasmas. Anyappropriate plasma source may be used, including DC, AC, RF, VHF,combinatorial PECVD and microwave sources may be used. Some non-limitingexamples of useful PECVD tools include hollow cathode tube PECVD,magnetron confined PECVD, inductively coupled plasma chemical vapordeposition (ICP-PECVD, sometimes called HDPECVD, ICP-CVD or HDCVD), andexpanding thermal plasma chemical vapor deposition (ETP-PECVD).

PECVD process conditions (temperatures, pressures, precursor gases,carrier gasses, dopant gases, flow rates, energies, and the like) canvary according to the particular process and tool used, as is well knownin the art

In some implementations, the PECVD process is an expanding thermalplasma chemical vapor deposition (ETP-PECVD) process. In such a process,a plasma generating gas is passed through a direct current arc plasmagenerator to form a plasma, with a web or other substrate including thecurrent collector optionally in an adjoining vacuum chamber. A siliconsource gas is injected into the plasma, with radicals generated. Theplasma is expanded via a diverging nozzle and injected into the vacuumchamber and toward the substrate. An example of a plasma generating gasis argon (Ar). In some embodiments, the ionized argon species in theplasma collide with silicon source molecules to form radical species ofthe silicon source, resulting in deposition onto the current collector.Example ranges for voltages and currents for the DC plasma source are 60to 80 volts and 40 to 70 amperes, respectively.

Any appropriate silicon source may be used to deposit silicon layers,including silane (SiH₄), dichlorosilane (H₂SiCl₂), monochlorosilane(H₃SiCl), trichlorosilane (HSiCl₃), silicon tetrachloride (SiCl₄), anddiethylsilane to form the silicon layers. Depending on the gas used, thesilicon layer may be formed by decomposition or reaction with anothercompound, such as by hydrogen reduction. Depending on the gas(es) used,the silicon layer may be formed by decomposition or reaction withanother compound, such as by hydrogen reduction. In some embodiments,the gases may include a silicon source such as silane, a noble gas suchas helium, argon, neon, or xenon, optionally one or more dopant gases,and substantially no hydrogen. In some embodiments, the gases mayinclude argon, silane, and hydrogen, and optionally some dopant gases.In some embodiments the gas flow ratio of argon relative to the combinedgas flows for silane and hydrogen is at least 3.0, alternatively atleast 4.0. In some embodiments, the gas flow ratio of argon relative tothe combined gas flows for silane and hydrogen is in a range of 3-5,alternatively 5-10, alternatively 10-15, alternatively 15-20, or anycombination of contiguous ranges thereof. In some embodiments, the gasflow ratio of hydrogen gas to silane gas is in a range of 0-0.1,alternatively 0.1-0.2, alternatively 0.2-0.5, alternatively 0.5-1,alternatively 1-2, alternatively 2-5, or any combination of contiguousranges thereof. In some embodiments, higher porosity silicon may beformed and/or the rate of silicon deposition may be increased when thegas flow ratio of silane relative to the combined gas flows of silaneand hydrogen increases. In some embodiments a dopant gas is borane orphosphine, which may be optionally mixed with a carrier gas. In someembodiments, the gas flow ratio of dopant gas (e.g., borane orphosphine) to silicon source gas (e.g., silane) is in a range of0.0001-0.0002, alternatively 0.0002-0.0005, alternatively 0.0005-0.001,alternatively 0.001-0.002, alternatively 0.002-0.005, alternatively0.005-0.01, alternatively 0.01-0.02, alternatively 0.02-0.05,alternatively 0.05-0.10, or any combination of contiguous rangesthereof. Such gas flow ratios described above may refer to the relativegas flow, e.g., in standard cubic centimeter per minute (SCCM). In someembodiments, the PECVD deposition conditions and gases may be changedover the course of the deposition.

In some embodiments, the temperature at the current collector during atleast a portion of the time of PECVD deposition is in a range of 100° C.to 200° C., alternatively 200° C. to 300° C., alternatively 300° C. to400° C., alternatively 400° C. to 500° C., alternatively 500° C. to 600°C., alternatively 600° C. to 700° C. or any combination of contiguousranges thereof. In some embodiments, the temperature may vary during thetime of PECVD deposition. For example, the temperature during earlytimes of the PECVD may be higher than at later times. Alternatively, thetemperature during later times of the PECVD may be higher than atearlier times.

As mentioned, in some embodiments the lithium storage layer may bedeposited using the same or different CVD process as used to form thelithium storage filamentary structures. A “CVD process” may refer tocertain process conditions that are used to control the deposition, inparticular, temperature, precursor material, gas flow rate, pressure,and plasma energy (if applicable). In some embodiments, the lithiumstorage layer may be deposited concurrently with formation of thelithium storage filamentary structures, or in separate steps, whereeither side may be deposited or formed prior to the other. Ifconcurrently, the CVD tool, for example a PECVD tool, may be configuredto deposit the desired lithium storage layer on the first side, and formthe desired lithium storage filamentary structures on the second side.Concurrent deposition may use substantially the same CVD processconditions for both sides. In some embodiments, “substantially the same”may include when the two CVD process temperatures are within 20° C., thesame precursors and carrier gases are used, the gas flow rates arewithin 20%, the chamber pressures are with 20%, and the applied plasmaenergies (if applicable) are within 20%. In some embodiments, eventhough concurrently deposited, the first side and second side CVDprocesses may be different, e.g., due to different localized gas flows,precursor gas mixtures, plasma energies or the like.

Other Anode Features

The anode may optionally include various additional layers and features.The current collector may include one or more features to ensure that areliable electrical connection can be made. In some embodiments, asupplemental layer 150-1 may be provided over the surface of the lithiumstorage layer, as shown in FIG. 6. Alternatively, or in addition, asupplemental layer 150-2 may be provided over the lithium storagefilamentary structures 122. In some embodiments, the supplemental layermay be a protection layer to enhance lifetime or physical durability.The supplemental layer may be an oxide formed from the lithium storagematerial itself, e.g., silicon dioxide or silicon nitride in the case ofsilicon. A supplemental layer may be deposited, for example, by ALD,CVD, PECVD, evaporation, sputtering, solution coating, ink jet, or anymethod that is compatible with the anode. In some embodiments, asupplemental layer is deposited in the same CVD or PECVD device as usedto form the lithium storage layer or lithium storage filamentarystructures. For example, a silicon dioxide or silicon nitridesupplemental layer may be formed by introducing an oxygen- ornitrogen-containing gas along with the silicon precursor gas used toform the lithium storage layer or lithium storage filamentarystructures. In some embodiments the supplemental layer may include boronnitride or silicon carbide. In some embodiments, a supplemental layermay include a metal compound as described below.

A supplemental layer should be reasonably conductive to lithium ions andpermit lithium ions to move into and out of the lithium storage layerduring charging and discharging. In some embodiments, the lithium ionconductivity of a supplemental layer is at least 10⁻⁹ S/cm,alternatively at least 10⁻⁸ S/cm, alternatively at least 10⁻⁷ S/cm,alternatively at least 10⁻⁶ S/cm. In some embodiments, the supplementallayer acts as a solid-state electrolyte. In some embodiments, thesupplemental layer(s) are less electrically conductive than the lithiumstorage structure so that little or no electrochemical reduction oflithium ions to lithium metal occurs at the supplementallayer/electrolyte interface. In addition to providing protection fromelectrochemical reactions, a multiple supplemental layer structure mayprovide superior structural support. In some embodiments, although thesupplemental layers may flex and may form fissures when the lithiumstorage layer expands during lithiation, crack propagation can bedistributed between the layers to reduce direct exposure of the lithiumstorage structure to the bulk electrolyte. For example, a fissure in thesecond supplemental layer may not align with a fissure in the firstsupplemental layer. Such an advantage may not occur if just one thicksupplemental layer is used. In an embodiment, the second supplementallayer may be formed of a material having higher flexibility than thefirst supplemental layer.

In some embodiments, a supplemental layer may include silicon nitride,e.g., substantially stoichiometric silicon nitride where the ratio ofnitrogen to silicon is in a range of 1.33 to 1.25. A supplemental layercomprising silicon nitride may have an average thickness in a range ofabout 0.5 nm to 1 nm, alternatively 1 nm to 2 nm, alternatively 2 nm to10 nm, alternatively 10 nm to 20 nm, alternatively 20 nm to 30 nm,alternatively 30 nm to 40 nm, alternatively 40 nm to 50 nm, or anycombination of contiguous ranges thereof. Silicon nitride may bedeposited by an atomic layer deposition (ALD) process or by a CVDprocess. In some embodiments, the lithium storage layer includes silicondeposited by some type of CVD process as described above, and at theend, a nitrogen gas source is added to the CVD deposition chamber alongwith the silicon source.

In some embodiments, a supplemental layer may include silicon dioxide,e.g., substantially stoichiometric silicon dioxide where the ratio ofoxygen to silicon is in a range of 2.0 to 1.9. A supplemental layercomprising silicon dioxide may have an average thickness in a range ofabout 2 nm to 10 nm, alternatively 10 nm to 30 nm, alternatively 30 nmto 50 nm, alternatively 50 nm to 70 nm, alternatively 70 nm to 100 nm,alternatively 100 nm to 150 nm, alternatively 150 nm to 200 nm, or anycombination of contiguous ranges thereof. Silicon dioxide may bedeposited by an atomic layer deposition (ALD) process or by a CVDprocess. In some embodiments, the lithium storage layer includes silicondeposited by some type of CVD process as described above, and at theend, an oxygen-containing gas source is added to the CVD depositionchamber along with the silicon source.

In some embodiments, a supplemental layer may include siliconoxynitride, e.g., a substantially stoichiometric oxynitride of silicon(SiO_(x)N_(y)) wherein the sum of 0.5x and 0.75y is in a range of 1.00to 0.95. A supplemental layer comprising silicon nitride may have anaverage thickness in a range of about 0.5 nm to 1 nm, alternatively 1 nmto 2 nm, alternatively 2 nm to 10 nm, alternatively 10 nm to 20 nm,alternatively 20 nm to 30 nm, alternatively 30 nm to 40 nm,alternatively 40 nm to 50 nm, alternatively 50 nm to 70 nm,alternatively 70 nm to 100 nm, alternatively 100 nm to 150 nm, or anycombination of contiguous ranges thereof. In some embodiments, siliconoxynitride may be provided by a CVD process, including but not limitedto, a PECVD process.

In some embodiments, silicon nitride, silicon dioxide, or siliconoxynitride may be deposited by an atomic layer deposition (ALD) processor by a CVD process. In some embodiments, the lithium storage layerincludes silicon deposited by some type of CVD process as describedabove, and at the end, a nitrogen- and/or an oxygen-containing gassource is added to the CVD deposition chamber along with the siliconsource.

In some embodiments a supplemental layer may include a metal compound.In some embodiments, the metal compound includes a metal oxide, metalnitride, or metal oxynitride, e.g., those containing aluminum, titanium,vanadium, zirconium, or tin, or mixtures thereof. In some embodiments, asupplemental layer including a metal oxide, metal nitride, or metaloxynitride, may have an average thickness of less than about 100 nm, forexample, in a range of about 0.5 nm to about 1 nm, alternatively about 1nm to about 2 nm, alternatively 2 nm to 10 nm, alternatively 10 nm to 20nm, alternatively 20 nm to 30 nm, alternatively 30 nm to 40 nm,alternatively 40 nm to 50 nm, or any combination of contiguous rangesthereof. The metal oxide, metal nitride, or metal oxynitride may includeother components or dopants such as transition metals, phosphorous orsilicon.

In some embodiments, the metal compound may include a lithium-containingmaterial such as lithium phosphorous oxynitride (LIPON), a lithiumphosphate, a lithium aluminum oxide, or a lithium lanthanum titanate. Insome embodiments, the thickness of supplemental layer including alithium-containing material may be in a range of 0.5 nm to 200 nm,alternatively 1 nm to 10 nm, alternatively 10 nm to 20 nm, alternatively20 nm to 30 nm, alternatively 30 nm to 40 nm, alternatively 40 nm to 50nm, alternatively 50 nm to 100 nm, alternatively 100 to 200 nm, or anycombination of contiguous ranges thereof.

In some embodiments the metal compound may be deposited by a processcomprising ALD, thermal evaporation, sputtering, or e-beam evaporation.ALD is a thin-film deposition technique typically based on thesequential use of a gas phase chemical process. The majority of ALDreactions use at least two chemicals, typically referred to asprecursors. These precursors react with the surface of a material one ata time in a sequential, self-limiting, manner. Through the repeatedexposure to separate precursors, a thin film is deposited, often in aconformal manner. In addition to conventional ALD systems, so-calledspatial ALD (SALD) methods and materials can be used, e.g., as describedU.S. Pat. No. 7,413,982, the entire contents of which are incorporatedby reference herein for all purposes. In certain embodiments, SALD canbe performed under ambient conditions and pressures and have higherthroughput than conventional ALD systems.

In some embodiments, the process for depositing the metal compound mayinclude electroless deposition, contact with a solution, contact with areactive gas, or electrochemical methods. In some embodiments, a metalcompound may be formed by depositing a metallic layer (including but notlimited to thermal evaporation, CVD, sputtering, e-beam evaporation,electrochemical deposition, or electroless deposition) followed bytreatment to convert the metal to the metal compound (including but notlimited to, contact with a reactive solution, contact with an oxidizingagent, contact with a reactive gas, or a thermal treatment).

The supplemental layer may include an inorganic-organic hybrid structurehaving alternating layers of metal oxide and bridging organic materials.These inorganic-organic hybrid structures are sometimes referred to as“metalcone”. Such structures can be made using a combination of atomiclayer deposition to apply the metal compound and molecular layerdeposition (MLD) to apply the organic. The organic bridge is typically amolecule having multiple functional groups. One group can react with alayer comprising a metal compound and the other group is available toreact in a subsequent ALD step to bind a new metal. There is a widerange of reactive organic functional groups that can be used including,but not limited to hydroxy, carboxylic acid, amines, acid chlorides andanhydrides. Almost any metal compound suitable for ALD deposition can beused. Some non-limiting examples include ALD compounds for aluminum(e.g., trimethyl aluminum), titanium (e.g., titanium tetrachloride),zinc (e.g., diethyl zinc), and zirconium(tris(dimethylamino)cyclopentadienyl zirconium). For the purposes of thepresent disclosure, this alternating sublayer structure of metaloxide/bridging organic is considered a single supplemental layer ofmetalcone. When the metal compound includes aluminum, such structuresmay be referred to as an alucone. Similarly, when the metal compoundincludes zirconium, such structures may be referred to as a zircone.Further examples of inorganic-organic hybrid structures that may besuitable as a supplemental layer may be found in U.S. Pat. No.9,376,455, and US patent publications 2019/0044151 and 2015/0072119, theentire contents of which are incorporated herein by reference.

In some embodiments, a supplemental layer having a metalcone may have athickness in a range of 0.5 nm to 200 nm, alternatively 1 nm to 10 nm,alternatively 10 nm to 20 nm, alternatively 20 nm to 30 nm,alternatively 30 nm to 40 nm, alternatively 40 nm to 50 nm,alternatively 50 nm to 100 nm, alternatively 100 to 200 nm, or anycombination of contiguous ranges thereof.

In some embodiments a supplemental layer (a first, a second, or anadditional supplemental layer) may include boron nitride or siliconcarbide and may have an average thickness of less than about 100 nm, forexample, in a range of about 0.5 nm to about 1 nm, alternatively about 1nm to about 2 nm, alternatively 2 nm to 10 nm, alternatively 10 nm to 20nm, alternatively 20 nm to 30 nm, alternatively 30 nm to 40 nm,alternatively 40 nm to 50 nm, or any combination of contiguous rangesthereof.

In some embodiments the anode is at least partially pre-lithiated, i.e.,the lithium storage layer and/or the lithium storage filamentarystructures include some lithium prior to battery assembly, that is,prior to combining the anode with a cathode in a battery cell. Note thata “lithiated storage layer” simply means that at least some of thepotential storage capacity the lithium storage layer is filled, but notnecessarily all. Similarly, “lithiated storage filamentary structures”simply means that at least some of the potential storage capacity thelithium storage filamentary structures is filled, but not necessarilyall. In some embodiments, the lithiated storage layer may includelithium in a range of 1% to 10% of the theoretical lithium storagecapacity of the lithium storage layer, alternatively 10% to 20%,alternatively, 20% to 30%, alternatively 30% to 40%, alternatively 40%to 50%, alternatively 50% to 60%, alternatively 60% to 70%,alternatively 70% to 80%, alternatively 80% to 90%, alternatively 90% to100%, or any combination of contiguous ranges thereof. In someembodiments, the metal oxide material may capture some of the lithium,and one may need to account for such capture to achieve the desiredlithium range in the lithiated storage layer. In some embodiments, thelithiated storage filamentary structures may include lithium in a rangeof 1% to 10% of the theoretical lithium storage capacity of the lithiumstorage filamentary structures, alternatively 10% to 20%, alternatively,20% to 30%, alternatively 30% to 40%, alternatively 40% to 50%,alternatively 50% to 60%, alternatively 60% to 70%, alternatively 70% to80%, alternatively 80% to 90%, alternatively 90% to 100%, or anycombination of contiguous ranges thereof.

In some embodiments prelithiation may include depositing lithium metalover the lithium storage layer and/or over the lithium storagefilamentary structures, e.g., by evaporation, e-beam or sputtering.Alternatively, prelithiation may include contacting the anode with areductive lithium organic compound, e.g., lithium naphthalene,n-butyllithium or the like. In some embodiments, prelithiation mayinclude incorporating lithium by electrochemical reduction of lithiumion in prelithiation solution.

In some embodiments, prelithiation includes physical contact of thelithium storage layer and/or the lithium storage filamentary structureswith a lithiation material. The lithiation material may include areducing lithium compound, lithium metal or a stabilized lithium metalpowder, any of which may optionally be provided as a coating on alithium transfer substrate. The lithium transfer substrate may include ametal (e.g., as a foil), a polymer, a ceramic, or some combination ofsuch materials, optionally in a multilayer format. In some embodiments,such lithiation material may be provided on at least one side of acurrent separator that faces the anode, i.e., the current separator alsoacts as a lithium transfer substrate. Stabilized lithium metal powders(“SLMP”) typically have a phosphate, carbonate or other coating over thelithium metal particles, e.g. as described in U.S. Pat. Nos. 8,377,236,6,911,280, 5,567,474, 5,776,369, and 5,976,403, the entire contents ofwhich are incorporated herein by reference. In some embodiments SLMPsmay require physical pressure to break the coating and allowincorporation of the lithium into the lithium storage layer and/or thelithium storage filamentary structures. In some embodiments, otherlithiation materials may be applied with pressure and/or heat to promotelithium transfer into the lithium storage layer, optionally through oneor more supplemental layers. In some embodiments a pressure appliedbetween an anode and a lithiation material may be at least 200 kPa,alternatively at least 1000 kPa, alternatively at least 5000 kPa.Pressure may be applied, for example, by calendering, pressurizedplates, or in the case of a lithiation material coating on a currentseparator, by assembly into battery having confinement or otherpressurizing features.

In some embodiments, prelithiation includes thermally treating thelithium storage layer and/or the lithium storage filamentary structuresduring lithium incorporation, after lithium incorporation, or bothduring and after. The thermal treatment may assist in the incorporationof the lithium, for example by promoting lithium diffusion. In someembodiments, thermally treating includes exposing the anode to atemperature in a range of 50° C. to 100° C., alternatively 100° C. to150° C., alternatively 150° C. to 200° C., alternatively 200° C. to 250°C., alternatively 250° C. to 300° C., or alternatively 300° C. to 350°C. In some embodiments, thermal treatment may be done under controlledatmosphere, e.g., under vacuum or argon atmosphere to avoid unwantedreactions with oxygen, nitrogen, water or other reactive gases.

In some embodiments, prelithiation may soften the lithium storage layerand/or the lithium storage filamentary structures, for example, due tothe formation of a lithium-silicon alloy. This softening may causeproblems in some processes, for example, roll-to-roll processes wherebythe softened lithium storage layer and/or the lithium storagefilamentary structures begin to stick to rollers or to itself duringwinding. In some embodiments, by providing one or more supplementallayers prior to prelithiation, or by providing a lithium-ion conductinglayer after prelithiation, the structural integrity and processabilityof the anode may be substantially improved. In some embodiments, thesupplemental layer(s) may act as a harder interface with other surfacesto prevent or reduce contact of such surfaces with the softened lithiumstorage

In some embodiments, only the lithium storage layer side of the anode isprelithiated. Prelithiation is expected to cause silicon-containinglithium storage layer to expand. In some embodiments, the expansion mayinduce stress on the lithium storage layer. As shown in FIG. 7, suchstress in the lithiated storage layer 107-L may be readily released byallowing the anode to bend. Such bending may create stress on the secondside of the electrically conductive substrate, but the discontinuousnature of the lithium storage filamentary structures on the second sidemay readily absorb this stress better than if a second lithium storagelayer was instead provided on the second side. In some embodiments, thelithium storage filamentary structures are also prelithiated to formlithiated filamentary structures. In some embodiments, even in thelithiated state, the second side may still readily absorb possiblestresses from the lithiated storage layer 107-L. In some embodiments, ananode where at least the lithium storage layer is prelithiated, andoptionally also having the lithium storage filamentary structuresprelithiated, may be stored in roll format, or provided into a batteryhaving a jelly roll structure, where the first side 103-1 of theelectrically conductive substrate 103 faces outwardly with respect tothe roll center and the second side 103-2 faces inwardly.

In some embodiments, only the lithium storage filamentary structures areprelithiated. In some embodiments, the lithiated filamentary structuresmay absorb expansion stresses with minimal stress transference to thecurrent collector.

In some embodiments the current collector may include vias or have amesh structure so that both sides are in fluid communication withrespect to a solution-based electrolyte when assembled into a battery.In this way, a non-prelithiated side of the anode may partly benefitfrom the lithiated side of the anode (e.g., with respect to overcomingfirst cycle lithium losses in the system), even when assembled intomultilayer stacks or a jellyroll form that include a cathode andseparator. In some embodiments, the cathode may have vias or a meshstructure.

Thermal treatments were discussed above with respect to prelithiationand the surface layer, but in some embodiments the anode may bethermally treated prior to battery assembly (after deposition of thelithium storage layer and lithium storage filamentary structures iscomplete, but before the anode is combined with a cathode in a batterycell), with or without a prelithiation step. In some embodiments,thermally treating the anode may improve adhesion of the various layers,improve charge capacity, improve charging rates, or improve electricalconductivity. In some embodiments, thermally treating the anode may bedone in a controlled environment, e.g., under vacuum, argon, or nitrogenhaving a low oxygen and water content (e.g., less than 100 ppm orpartial pressure of less than 10 Torr, alternatively less than 1 Torr,alternatively less than 0.1 Torr to prevent degradation). Herein, “undervacuum” generally refers to a reduced pressure condition wherein thetotal pressure of all gasses (e.g. in a vacuum oven) is less than 10Torr. Due to equipment limitations, the vacuum pressure is typicallygreater than about 10⁻⁸ Torr. In some embodiments, anode thermaltreatment may be carried out using an oven, a tube furnace, infraredheating elements, contact with a hot surface (e.g. a hot plate), orexposure to a flash lamp. The anode thermal treatment temperature andtime depend on the materials of the anode. In some embodiments, anodethermal treatment includes heating the anode to a temperature of atleast 50° C., optionally in a range of 50° C. to 600° C., alternatively100° C. to 250° C., alternatively 250° C. to 350° C., alternatively 350°C. to 450° C., alternatively 450° C. to 600° C., alternatively 600° C.to 700° C., alternatively 700° C. to 800° C., or any combination ofcontiguous ranges thereof. In some embodiments, the anode thermaltreatment time may be in a range of about 0.1 min to about 1 min,alternatively about 1 min to about 5 mins, alternatively about 5 mins toabout 10 mins, alternatively about 10 mins to about 30 minutes,alternatively about 30 mins to about 60 mins, alternatively about 60mins to about 90 mins, alternatively in a range of about 90 mins toabout 120 mins, or any combination of contiguous ranges thereof.

In some embodiments one or more processing steps described above may beperformed using roll-to-roll methods wherein the electrically conductivesubstrate is in the form of a rolled film, e.g., a roll of metal foil.In some embodiments, processing of the anode may include contact of thelithium storage layer with rollers or other conveyance or transportfeatures of the processing equipment, with less or no substantialcontact of the lithium storage filamentary structures with such rollersor other conveyance or transport features of the processing equipment.

Battery Features

The preceding description relates primarily to the anode/negativeelectrode of a lithium-ion battery (LIB). The LIB typically includes acathode/positive electrode, an electrolyte and a separator (if not usinga solid-state electrolyte). As is well known, batteries can be formedinto multilayer stacks of anodes and cathodes with an interveningseparator. Alternatively, a single anode/cathode stack can be formedinto a so-called jellyroll. Such structures are provided into anappropriate housing having desired electrical contacts.

In some embodiments, the battery may be constructed with confinementfeatures to limit expansion of the battery, e.g., as described in USpublished applications 2018/0145367 and 2018/0166735, the entirecontents of which are incorporated herein by reference. In someembodiments a physical pressure is applied between the anode andcathode, e.g., using a tensioned spring or clip, a compressible film orthe like. Confinement, pressure, or both may help ensure that the anoderemains in active contact with the current collector during formationand cycling, which may cause expansion and contraction of the lithiumstorage layer and/or the lithium storage filamentary structures.

FIG. 8 is a schematic cross-sectional view of a battery according tosome embodiments of the present disclosure. Battery 790 includes topplate 760, bottom plate 762, anode side plate 764 and cathode side plate766, which form part of a housing for the stack of anodes 700, cathodes740 and intervening separators 730. Anodes are attached to an anode bus720 which is connected to anode lead 722 that extends through anode sideplate 764. Cathodes are attached to a cathode bus 750 which is connectedto cathode lead 752 that extends through cathode side plate 766. Battery790 further includes electrolyte 780 which fills the space and saturatesthe separators 730. Top compression member 770 and lower compressionmember 772 apply physical pressure (arrows) between the anodes andcathodes. Compression members may be compressible films, e.g., made froma porous polymer or silicone. Alternatively, compression members mayinclude an array of compressible features, e.g., made from porouspolymer or silicone. Alternatively, the compression members may includesprings or an array of springs. Alternatively, compression members maycorrespond to two sides of a compression clip or clamp. In someembodiments, the separator may act as a compressible film. In someembodiments the top and bottom plates may be formed a material and/orstructured to resist deformation thereby confining battery swell.

Cathode

Positive electrode (cathode) materials include, but are not limited to,lithium metal oxides or compounds (e.g., LiCoO₂, LiFePO₄, LiMnO₂,LiNiO₂, LiMn₂O₄, LiCoPO₄, LiNi_(x)Co_(y)Mn_(z)O₂,LiNi_(x)Co_(Y)Al_(Z)O₂, LiFe₂(SO₄)₃, or Li₂FeSiO₄), carbon fluoride,metal fluorides such as iron fluoride (FeF₃), metal oxide, sulfur,selenium, sulfur-selenium and combinations thereof. Cathode activematerials are typically provided on, or in electrical communicationwith, an electrically conductive cathode current collector.

In some embodiments, a prelithiated anode of the present disclosure isused with cathode including sulfur, selenium, or both sulfur andselenium (collectively referred to herein as “chalcogen cathodes”). Insome embodiments, a prelithiated anode of the present disclosure may bepaired with a chalcogen cathode having an active material layer, whereinthe active material layer may include a carbon material and a compoundselected from the group consisting of Se, Se_(y)S_(x), Te_(y)S_(x),Te_(z)Se_(y)S_(x), and combinations thereof, where x, y and z are anyvalue between 0 and 1, the sum of y and x being 1, and the sum of z, yand x being 1, the compound impregnated in the carbon material , e.g.,as described in US published application 2019/0097275, which isincorporated by reference herein for all purposes. The compound may bepresent in an amount of 9-90% by weight based on the total weight of theactive material layer. In some embodiments, the chalcogen cathode activematerial layer further includes conductive carbon nanotubes to improveoverall conductivity and physical durability and may permit fastercharging and discharging. The presence of carbon nanotubes may furtherallow thicker coatings that have greater flexibility thereby allowinghigher capacity.

Chalcogen cathodes are generally paired with lithium metal anodes.However, lithium metal anodes are difficult to handle, prone todegradation, and may further allow formation of dangerous dendriticlithium that can lead to catastrophic shorts. In some embodiments,prelithiated anodes of the present disclosure can achieve equivalentenergy storage capacity of a pure lithium anode, but are much easier tohandle and less prone to form dendritic lithium, thus making them morecompatible with chalcogen cathodes.

In some embodiments, different cathode active material layers may beprovided on opposite sides of the cathode current collector such that,in the battery, a first cathode active material layer may face the anodelithium storage layer and a second cathode active material layer mayface the plurality of lithium storage filaments.

Current Separator

The current separator allows ions to flow between the anode and cathodebut prevents direct electrical contact. Such separators are typicallyporous sheets. Non-aqueous lithium-ion separators are single layer ormultilayer polymer sheets, typically made of polyolefins, especially forsmall batteries. Most commonly, these are based on polyethylene orpolypropylene, but polyethylene terephthalate (PET) and polyvinylidenefluoride (PVDF) can also be used. For example, a separator can have >30%porosity, low ionic resistivity, a thickness of ˜10 to 50 μm and highbulk puncture strengths. Separators may alternatively include glassmaterials, ceramic materials, a ceramic material embedded in a polymer,a polymer coated with a ceramic, or some other composite or multilayerstructure, e.g., to provide higher mechanical and thermal stability. Asmentioned, the separator may include a lithiation material such aslithium metal, a reducing lithium compound, or an SLMP material coatedat least on the side facing the anode.

Electrolyte

The electrolyte in lithium ion cells may be a liquid, a solid, or a gel.A typical liquid electrolyte comprises one or more solvents and one ormore salts, at least one of which includes lithium. During the first fewcharge cycles (sometimes referred to as formation cycles), the organicsolvent and/or the electrolyte may partially decompose on the negativeelectrode surface to form an SEI (Solid-Electrolyte-Interphase) layer.The SEI is generally electrically insulating but ionically conductive,thereby allowing lithium ions to pass through. The SEI may lessendecomposition of the electrolyte in the later charging cycles.

Some non-limiting examples of non-aqueous solvents suitable for somelithium ion cells include the following: cyclic carbonates (e.g.,ethylene carbonate (EC), fluoroethylene carbonate (FEC), propylenecarbonate (PC), butylene carbonate (BC) and vinylethylene carbonate(VEC)), vinylene carbonate (VC), lactones (e.g., gamma-butyrolactone(GBL), gamma-valerolactone (GVL) and alpha-angelica lactone (AGL)),linear carbonates (e.g., dimethyl carbonate (DMC), methyl ethylcarbonate (MEC, also commonly abbreviated EMC), diethyl carbonate (DEC),methyl propyl carbonate (MPC), dipropyl carbonate (DPC), methyl butylcarbonate (NBC) and dibutyl carbonate (DBC)), ethers (e.g.,tetrahydrofuran (THF), 2-methyltetrahydrofuran, 1,4-dioxane,1,2-dimethoxyethane (DME), 1,2-diethoxyethane and 1,2-dibutoxyethane),nitriles (e.g., acetonitrile and adiponitrile) linear esters (e.g.,methyl propionate, methyl pivalate, butyl pivalate and octyl pivalate),amides (e.g., dimethyl formamide), organic phosphates (e.g., trimethylphosphate and trioctyl phosphate), organic compounds containing an S═Ogroup (e.g., dimethyl sulfone and divinyl sulfone), and combinationsthereof.

Non-aqueous liquid solvents can be employed in combination. Examples ofthese combinations include combinations of cyclic carbonate-linearcarbonate, cyclic carbonate-lactone, cyclic carbonate-lactone-linearcarbonate, cyclic carbonate-linear carbonate-lactone, cycliccarbonate-linear carbonate-ether, and cyclic carbonate-linearcarbonate-linear ester. In some embodiments, a cyclic carbonate may becombined with a linear ester. Moreover, a cyclic carbonate may becombined with a lactone and a linear ester. In some embodiments, theweight ratio, or alternatively the volume ratio, of a cyclic carbonateto a linear ester is in a range of 1:9 to 10:1, alternatively 2:8 to 7:3

A salt for liquid electrolytes may include one or more of the followingnon-limiting examples: LiPF₆, LiBF₄, LiClO₄, LiAsF₆, LiN(CF₃SO₂)₂,LiN(C₂F₅SO₂)₂, LiCF₃SO₃, LiC(CF₃SO₂)₃, LiPF₄(CF₃)₂, LiPF₃(C₂F₅)₃,LiPF₃(CF₃)₃, LiPF₃ (iso-C₃F₇)₃, LiPF₅(iso-C₃F₇), lithium salts havingcyclic alkyl groups (e.g., (CF₂)₂(SO₂)_(2x)Li and (CF₂)₃(SO₂)_(2x)Li),and combinations thereof. Common combinations include: LiPF₆ and LiBF₄;LiPF₆ and LiN(CF₃SO₂)₂; and LiBF₄ and LiN(CF₃SO₂)₂.

In some embodiments, the total concentration of salt in a liquidnon-aqueous solvent (or combination of solvents) is at least 0.3 M,alternatively at least 0.7M. The upper concentration limit may be drivenby a solubility limit and operational temperature range. In someembodiments, the concentration of salt is no greater than about 2.5 M,alternatively no more than about 1.5 M.

In some embodiments, the battery electrolyte includes a non-aqueousionic liquid and a lithium salt.

A solid-state electrolyte may be used without the separator because itserves as the separator itself. It is electrically insulating, ionicallyconductive, and electrochemically stable. In the solid electrolyteconfiguration, a lithium containing salt, which could be the same as forthe liquid electrolyte cells described above, is employed but ratherthan being dissolved in an organic solvent, it is held in a solidmatrix, which may include inorganic materials or a polymer composite. Insome embodiments, a solid-state electrolyte may be vapor deposited,solution-coated, melt-coated or a combination thereof. Examples of solidpolymer electrolytes may be ionically conductive polymers prepared frommonomers containing atoms having lone pairs of electrons available forthe lithium ions of electrolyte salts to attach to and move betweenduring conduction, such as polyvinylidene fluoride (PVDF) or chloride orcopolymer of their derivatives, poly(chlorotrifluoroethylene),poly(ethylene-chlorotrifluoro-ethylene), or poly(fluorinatedethylene-propylene), polyethylene oxide (PEO) and oxymethylene linkedPEO, PEO-PPO-PEO crosslinked with trifunctional urethane,poly(bis(methoxy-ethoxy-ethoxide))-phosphazene (MEEP), triol-type PEOcrosslinked with difunctional urethane,poly((oligo)oxyethylene)methacrylate-co-alkali metal methacrylate,polyacrylonitrile (PAN), polymethylmethacrylate (PMMA),polymethylacrylonitrile (PMAN), polysiloxanes and their copolymers andderivatives, acrylate-based polymer, other similar solvent-freepolymers, combinations of the foregoing polymers either condensed orcross-linked to form a different polymer, and physical mixtures of anyof the foregoing polymers. Other less conductive polymers that may beused in combination with the above polymers to improve the strength ofthin laminates include: polyester (PET), polypropylene (PP),polyethylene naphthalate (PEN), polyvinylidene fluoride (PVDF),polycarbonate (PC), polyphenylene sulfide (PPS), andpolytetrafluoroethylene (PTFE). Such solid polymer electrolytes mayfurther include a small amount of organic solvents listed above. Thepolymer electrolyte may be an ionic liquid polymer. Such polymer-basedelectrolytes can be coated using any number of conventional methods suchas curtain coating, slot coating, spin coating, inkjet coating, spraycoating or other suitable method.

Additives may be included in the electrolyte to serve various functions.For example, additives such as polymerizable compounds having anunsaturated double bond may be added to stabilize or modify the SEI.Certain amines or borate compounds can act as cathode protection agents.Lewis acids can be added to stabilize fluorine-containing anion such asP₆ ⁻. Safety protection agents include those to protect overcharge,e.g., anisoles, or act as fire retardants, e.g., alkyl phosphates.

In some embodiments, the original, non-cycled anode may undergostructural or chemical changes during electrochemicalcharging/discharging, for example, from normal battery usage or from anearlier “electrochemical formation step”. As is known in the art, anelectrochemical formation step is commonly used to form an initial SEIlayer and involves relatively gentle conditions of low current andlimited voltages. The modified anode prepared in part from suchelectrochemical charging/discharging cycles may still have excellentperformance properties, despite such structural and/or chemical changesrelative to the original, non-cycled anode.

EXAMPLES Example 1 Current Collector

A current collector was prepared by oxidation of a 16 μm thick nickelfoil. The foil was provided into a muffle furnace under air at roomtemp, heated to 700° C. and held there for 30 minutes. The furnace wasturned off and the sample was allowed to cool within the furnace. Thelayer of nickel oxide was approximately 0.2-0.6 μm thick. Example 1Current Collector may correspond to the first side of an electricallyconductive substrate according to some embodiments of the presentdisclosure.

Example 2 Current Collector

The same kind of nickel foil as used in the Example 1 Current Collectorsimply cleaned with an IPA wipe and not subjected to any oxidationtreatments. Example 2 Current Collector may correspond to the secondside of an electrically conductive substrate according to someembodiments of the present disclosure.

Silicon Deposition

Silicon was concurrently deposited over the example current collectorsusing expanding thermal PECVD to form corresponding Example Anode 1(from Example 1 Current Collector) and Example Anode 2 (from Example 2Current Collector. The formation gases were silane at about 0.20 slm(standard liters per minute) and hydrogen at about 0.20 slm, along withan argon carrier gas at about 2 slm. The process pressure was about0.145 mbar.

Characterization

ICP-AES analysis showed Anode 1 had about 1.2 mg/cm² of total siliconand Anode 2 had about 2.4 mg/cm² of total silicon. In the case of Anode2, some of this silicon was in the form of nickel silicide, which haslower lithium storage capacity than amorphous silicon.

Anode 1 had a silvery, metallic appearance, although not mirror-like. Incontrast, Anode 2 had a black appearance. Microstructure differencesbetween the anodes are readily apparent as shown in FIGS. 9-10. FIG. 9Ais an SEM top view of Anode 1, and for reference, 9B is an SEMcross-sectional view. Anode 1 includes a continuous porous lithiumstorage layer. Unlike Anode 2, there is no evidence of lithium storagefilamentary structures. FIG. 9B shows that the continuous porous lithiumstorage layer may have some vertical fissures or pockets, but there islateral connectivity and it is substantially free of nanostructures.Other analyses showed that this layer includes primarily amorphoussilicon. FIG. 10 is an SEM top view of Anode 2 showing the plurality oflithium storage filamentary structures that formed having a maximumwidth generally in a range of about 2 to 3 μm. Unlike Anode 1, there isno evidence of a continuous silicon layer. Other analyses showed thatthe Anode 2 structures included nickel silicides and amorphous silicon.

When tested in half cells, both anodes showed reasonable cycle life andlithium storage capacity.

Although Anode 1 and Anode 2 were separate anodes, the data clearly showthat anodes of the present disclosure having a lithium storage layer onone side and lithium storage filamentary structures on the other sidecan be made simply, and concurrently, using the same PECVD process onboth sides of the electrically conductive substrate. As mentioned, thelithium storage layer and the lithium storage filamentary structures mayinstead be made under different CVD process conditions, or in separatesteps, for example, to optimize the performance of each side.

In some embodiments, the original, non-cycled anode may undergostructural or chemical changes during electrochemicalcharging/discharging, for example, from normal battery usage or from anearlier “electrochemical formation step”. As is known in the art, anelectrochemical formation step is commonly used to form an initial SEIlayer and involves relatively gentle conditions of low current andlimited voltages. The modified anode prepared in part from suchelectrochemical charging/discharging cycles may still have excellentperformance properties, despite such structural and/or chemical changesrelative to the original, non-cycled anode.

Although the present anodes have been discussed with reference tobatteries, in some embodiments the present anodes may be used in hybridcapacitor devices. Relative to conventional anodes, the anodes of thepresent disclosure may have one or more of at least the followingunexpected advantages: comparable or improved stability at aggressive ≥1C charging rates; higher overall areal charge capacity; highergravimetric charge capacity; higher volumetric charge capacity; improvedphysical durability; simplified manufacturing process; and/or a morereproducible manufacturing process.

Some non-limiting representative embodiments are listed below.

1. An anode for an energy storage device comprising:

a current collector comprising an electrically conductive substrate anda surface layer overlaying a first side of the electrically conductivesubstrate;

a lithium storage layer overlaying the surface layer; and

a plurality of lithium storage filamentary structures in contact with asecond side of the electrically conductive substrate, the second sideopposite the first side.

2. The anode of embodiment 1, wherein the surface layer comprises ametal oxide.

3. The anode of embodiment 2, wherein the metal oxide comprises atransition metal oxide.

4. The anode of embodiment 2 or 3, wherein the metal oxide comprises anoxide of nickel, an oxide of copper, an oxide of titanium, or acombination thereof.

5. The anode according to any of embodiments 1-4, wherein the surfacelayer comprises a metal chalcogenide comprising at least one of sulfuror selenium.

6. The anode of embodiment 5, wherein the metal chalcogenide comprises atransition metal sulfide, a transition metal polysulfide, a metaltransition selenide, or a transition metal polyselenide.

7. The anode of embodiment 5 or 6, wherein the metal chalcogenide is acopper chalcogenide.

8. The anode according to any of embodiments 1-7, wherein the surfacelayer has an average thickness in a range of in a range of 0.02 μm to 2μm.

9. The anode according to any of embodiments 1-8, wherein theelectrically conductive substrate comprises stainless steel, titanium,nickel, copper, a conductive carbon, or a combination thereof

10. The anode according to any of embodiments 1-9, wherein the lithiumstorage layer is a continuous porous lithium storage layer.

11. The anode according to any of embodiments 1-10, wherein the lithiumstorage layer has a total content of silicon, germanium, or acombination thereof of at least 40 atomic %.

12. The anode according to any of embodiments 1-11, wherein the lithiumstorage layer includes less than 10 atomic % carbon.

13. The anode according to any of embodiments 1-12, wherein the lithiumstorage layer is substantially free of nanostructures.

14. The anode according to any of embodiment 1-13, wherein the lithiumstorage layer is a continuous porous lithium storage layer comprisingamorphous silicon having an areal density of at least 0.2 mg/cm² and thetotal content of silicon is at least 40 atomic %.

15. The anode according to any of embodiment 1-14, wherein the lithiumstorage layer has an average thickness in a range from 0.5 μm to 40 μm.

16. The anode according to any of embodiment 1-15, wherein the lithiumstorage layer is a continuous porous lithium storage layer having anaverage density from 1.1 g/cm³ to 2.25 g/cm³ and comprises at least 85atomic % amorphous silicon.

17. The anode according to any of embodiments 1-16, wherein theplurality of lithium storage filamentary structures has an aspect ratioof at least 2.

18. The anode according to any of embodiments 1-17, wherein theplurality of lithium storage filamentary structures has an averageheight in a range of 0.2 μm to 100 μm

19. The anode according to any of embodiments 1-18, wherein theplurality of lithium storage filamentary structures has an averagemaximum width in a range of 0.1 μm to 10

20. The anode according to any of embodiments 1-19, wherein theplurality of lithium storage filamentary structures comprises silicon,germanium, tin, or a combination thereof.

21. The anode according to embodiment 20, wherein the plurality oflithium storage filamentary structures further comprises a transitionmetal silicide or transition metal alloy of germanium.

22. The anode according to any of embodiments 1-21, wherein each lithiumstorage filamentary structure of the plurality of lithium storagefilamentary structures comprises a core filament and a lithium storagecoating over the core filament.

23. The anode according to embodiment 22 wherein the core filamentcomprises a transition metal silicide or a transition metal alloy ofgermanium.

24. The anode according to embodiment 22 or 23, wherein the lithiumstorage coating comprises silicon, germanium, or a mixture thereof.

25. The anode according to any of embodiments 1-24, wherein the lithiumstorage filamentary structures have a total content of silicon,germanium, or a combination thereof of at least 40 atomic %.

26. The anode according to any of embodiments 1-25, wherein the secondside of the electrically conductive substrate comprises a filamentgrowth catalyst material.

27. The anode according to any of embodiments 1-26, wherein the lithiumstorage layer and the plurality of lithium storage filamentarystructures both comprise silicon.

28. The anode according to any of embodiments 1-27, wherein theelectrically conductive substrate comprises:

-   -   i) a first electrically conductive layer corresponding to the        first side of the electrically conductive substrate;    -   ii) a second electrically conductive layer corresponding to the        second side of the electrically conductive substrate; and    -   iii) an electrically insulating layer interposed between the        first electrically conductive layer and the second electrically        conductive layer.

29. A lithium-ion battery comprising a cathode and the anode accordingto any of embodiments 1-28.

30. The lithium-ion battery of embodiment 29, wherein the anode isprelithiated and the cathode comprises sulfur, selenium, or both sulfurand selenium.

31. The lithium-ion battery of embodiment 29 or 30, wherein the lithiumstorage layer is electrically addressable independently of the pluralityof lithium storage filamentary structures.

32. A method of making an anode for use in an energy storage device, themethod comprising:

providing a current collector comprising an electrically conductivesubstrate and a surface layer overlaying a first side of theelectrically conductive substrate, wherein a second side of theelectrically conductive substrate comprises a filament growth catalyst,wherein the second side is opposite the first side;

depositing a lithium storage layer onto the surface layer using a firstCVD process; and

forming a plurality of lithium storage filamentary structures on thesecond side of the electrically conductive substrate using a second CVDprocess.

33. The method of embodiment 32, wherein at least one of the first CVDprocess or the second CVD process comprises a PECVD process.

34. The method of embodiment 32 or 33, wherein the first CVD process isa first PECVD process and the second CVD process is a second PECVDprocess.

35. The method of according to any of embodiments 32-34, wherein thelithium storage layer comprises silicon, germanium, or a combinationthereof.

36. The method according to any of embodiments 32-35, wherein theplurality of lithium storage filamentary structures comprise silicon,germanium, or a combination thereof.

37. The method according to any of embodiments 32-36, wherein the firstCVD process is different than the second CVD process.

38. The method according to any of embodiments 32-36, wherein the firstCVD process is substantially the same as the second CVD process.

39. The method according to any of embodiments 32-38, wherein thelithium storage layer is deposited prior to or after forming theplurality of lithium storage filamentary structures.

40. The method according to any of embodiments 32-38, wherein depositingthe lithium storage layer is concurrent with forming the lithium storagefilamentary structures.

41. The method according to any of embodiments 32-40, wherein thesurface layer comprises a metal oxide.

42. The method of embodiment 41, wherein the metal oxide comprises atransition metal oxide.

43. The method of embodiment 40 or 41, wherein the metal oxide comprisesan oxide of nickel, an oxide of copper, an oxide of titanium, or acombination thereof.

44. The method according to any of embodiments 32-43, wherein thesurface layer comprises a metal chalcogenide comprising at least one ofsulfur or selenium.

45. The method of embodiment 44, wherein the metal chalcogenidecomprises a transition metal sulfide, a transition metal polysulfide, ametal transition selenide, or a transition metal polyselenide.

46. The method of embodiment 44 or 45, wherein the metal of thechalcogenide is a copper chalcogenide.

47. The method according to any of embodiments 32-46, wherein thesurface layer has an average thickness in a range of in a range of 0.02μm to 2 μm.

48. The method according to any of embodiments 32-47, wherein theelectrically conductive substrate comprises stainless steel, titanium,nickel, copper, a conductive carbon, or a combination thereof.

49. The method according to any of embodiments 32-48, wherein thefilament growth catalyst comprises nickel.

50. The method according to any of embodiments 32 -49, wherein thelithium storage layer is a continuous porous lithium storage layerhaving an average density from 1.1 g/cm³ to 2.25 g/cm³ and comprises atleast 85 atomic % amorphous silicon, and wherein the plurality oflithium storage filamentary structures comprise silicon.

51. A lithium-ion battery comprising a cathode and the anode made by themethod according to any of embodiments 32-50.

52. The lithium-ion battery of embodiment 51, wherein the anode isprelithiated and the cathode comprises sulfur, selenium, or both sulfurand selenium.

53. The lithium-ion battery of embodiment 52, wherein the cathodefurther comprises carbon nanotubes.

54. The lithium-ion battery according to any of embodiments 51-53,wherein the lithium storage layer is electrically addressableindependently of the plurality of lithium storage filamentarystructures.

The specific details of particular embodiments may be combined in anysuitable manner without departing from the spirit and scope ofembodiments of the invention. However, other embodiments of theinvention may be directed to specific embodiments relating to eachindividual aspect, or specific combinations of these individual aspects.

The above description of example embodiments of the invention has beenpresented for the purposes of illustration and description. It is notintended to be exhaustive or to limit the invention to the precise formdescribed, and many modifications and variations are possible in lightof the teaching above.

In the preceding description, for the purposes of explanation, numerousdetails have been set forth in order to provide an understanding ofvarious embodiments of the present technology. It will be apparent toone skilled in the art, however, that certain embodiments may bepracticed without some of these details, or with additional details.

Having described several embodiments, it will be recognized by those ofskill in the art that various modifications, alternative constructions,and equivalents may be used without departing from the spirit of theinvention. Additionally, a number of well-known processes and elementshave not been described in order to avoid unnecessarily obscuring thepresent invention. Additionally, details of any specific embodiment maynot always be present in variations of that embodiment or may be addedto other embodiments.

Where a range of values is provided, it is understood that eachintervening value, to the tenth of the unit of the lower limit unlessthe context clearly dictates otherwise, between the upper and lowerlimits of that range is also specifically disclosed. Each smaller rangebetween any stated value or intervening value in a stated range and anyother stated or intervening value in that stated range is encompassed.The upper and lower limits of these smaller ranges may independently beincluded or excluded in the range, and each range where either, neither,or both limits are included in the smaller ranges is also encompassedwithin the invention, subject to any specifically excluded limit in thestated range. Where the stated range includes one or both of the limits,ranges excluding either or both of those included limits are alsoincluded.

As used herein and in the appended claims, the singular forms “a”, “an”,and “the” include plural referents unless the context clearly dictatesotherwise. Thus, for example, reference to “a method” includes aplurality of such methods and reference to “the layer” includesreference to one or more layers and equivalents thereof known to thoseskilled in the art, and so forth. The invention has now been describedin detail for the purposes of clarity and understanding. However, itwill be appreciated that certain changes and modifications may bepracticed within the scope of the appended claims.

All publications, patents, and patent applications cited herein arehereby incorporated by reference in their entirety for all purposes.None is admitted to be prior art.

We claim:
 1. A method of making an anode for use in an energy storagedevice, the method comprising: providing a current collector comprisingan electrically conductive substrate and a surface layer overlaying afirst side of the electrically conductive substrate, wherein a secondside of the electrically conductive substrate comprises a filamentgrowth catalyst, wherein the second side is opposite the first side;depositing a lithium storage layer onto the surface layer using a firstCVD process; and forming a plurality of lithium storage filamentarystructures on the second side of the electrically conductive substrateusing a second CVD process.
 2. The method of claim 1, wherein the firstCVD process is a first PECVD process and the second CVD process is asecond PECVD process.
 3. The method of claim 1, wherein the lithiumstorage layer comprises a total content of silicon, germanium, or acombination thereof of at least 40 atomic %.
 4. The method of claim 1,wherein the plurality of lithium storage filamentary structurescomprises a total content of silicon, germanium, or a combinationthereof of at least 40 atomic %.
 5. The method of claim 1, wherein thefirst CVD process is different than the second CVD process.
 6. Themethod of claim 1, wherein the first CVD process is substantially thesame as the second CVD process.
 7. The method of claim 1, whereindepositing the lithium storage layer is concurrent with forming theplurality of lithium storage filamentary structures.
 8. The method ofclaim 1, wherein the surface layer comprises a transition metal oxide.9. The method of claim 1, wherein the surface layer comprises a metalchalcogenide comprising at least one of sulfur or selenium
 10. Themethod of claim 1, wherein the surface layer has an average thickness ina range of in a range of 0.02 μm to 2 μm.
 11. The method of claim 1,wherein the electrically conductive substrate comprises stainless steel,titanium, nickel, copper, a conductive carbon, or a combination thereof.12. The method of claim 1, wherein the electrically conductive substratecomprises: i) a first electrically conductive layer corresponding to thefirst side of the electrically conductive substrate; ii) a secondelectrically conductive layer corresponding to the second side of theelectrically conductive substrate and comprising the filament growthcatalyst; and iii) an electrically insulating layer interposed betweenthe first electrically conductive layer and the second electricallyconductive layer.
 13. The method of claim 1, wherein the filament growthcatalyst comprises nickel.
 14. The method of claim 1, wherein thelithium storage layer is a continuous porous lithium storage layerhaving an average density from 1.1 g/cm³ to 2.25 g/cm³ and comprising atleast 85 atomic % amorphous silicon, and wherein the lithium storagefilamentary structures comprise silicon.
 15. A lithium-ion batterycomprising the anode made by the method of claim 1 and a cathode. 16.The lithium-ion battery of claim 15, wherein the lithium storage layeris electrically addressable independently of the plurality of lithiumstorage filamentary structures.
 17. A method of making an anode for usein an energy storage device, the method comprising: providing a currentcollector comprising an electrically conductive substrate and atransition metal oxide layer overlaying a first side of the electricallyconductive substrate, wherein a second side of the electricallyconductive substrate comprises nickel as a filament growth catalyst, andwherein the second side is opposite the first side; depositing acontinuous porous lithium storage layer onto the transition metal oxidelayer using a first PECVD process, the continuous porous lithium storagelayer having an average density from 1.1 g/cm³ to 2.25 g/cm³ andcomprising at least 85 atomic % amorphous silicon; and concurrent withdepositing the continuous porous lithium storage layer, forming aplurality of lithium storage filamentary structures on the second sideof the electrically conductive substrate using second PECVD process, theplurality of lithium storage filamentary structures comprising a totalcontent of silicon of at least 40 atomic %.